From aixssd!darrenk@abs.net Thu Dec 5 10:30:53 1996
Received: from abs.net (root@u1.abs.net [207.114.0.130]) by candle.pha.pa.us (8.8.3/8.7.3) with ESMTP id KAA06591 for <maillist@candle.pha.pa.us>; Thu, 5 Dec 1996 10:30:43 -0500 (EST)
Received: from aixssd.UUCP (nobody@localhost) by abs.net (8.8.3/8.7.3) with UUCP id KAA01387 for maillist@candle.pha.pa.us; Thu, 5 Dec 1996 10:13:56 -0500 (EST)
Received: by aixssd (AIX 3.2/UCB 5.64/4.03)
id AA36963; Thu, 5 Dec 1996 10:10:24 -0500
Received: by ceodev (AIX 4.1/UCB 5.64/4.03)
id AA34942; Thu, 5 Dec 1996 10:07:56 -0500
Date: Thu, 5 Dec 1996 10:07:56 -0500
From: aixssd!darrenk@abs.net (Darren King)
Message-Id: <9612051507.AA34942@ceodev>
To: maillist@candle.pha.pa.us
Subject: Subselect info.
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Md5: jaWdPH2KYtdr7ESzqcOp5g==
Status: OR
> Any of them deal with implementing subselects?
There's a white paper at the www.sybase.com that might
help a little. It's just a copy of a presentation
given by the optimizer guru there. Nothing code-wise,
but he gives a few ways of flattening them with temp
tables, etc...
Darren
From vadim@sable.krasnoyarsk.su Thu Aug 21 23:42:50 1997
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id XAA04109
for <maillist@candle.pha.pa.us>; Thu, 21 Aug 1997 23:42:43 -0400 (EDT)
Received: from www.krasnet.ru (localhost [127.0.0.1]) by www.krasnet.ru (8.7.5/8.7.3) with SMTP id MAA04399; Fri, 22 Aug 1997 12:04:31 +0800 (KRD)
> this will allow to use 'outer' & 'inner' things for subselects
> latter, without confusion. My hope is that we may change Executor
Or may be use 'high' & 'low' for subselecs (to avoid confusion
with outter hoins).
> very easy by adding outer/inner plans/TupleSlots to
> EState, CommonState, JoinState, etc and by doing node
> processing in right order.
^^^^^^^^^^^^^^
Rule is easy:
1. Uncorrelated subselect - do 'low' plan node first
2. Correlated - do left/right first
- just some flag in structures.
Vadim
From owner-pgsql-hackers@hub.org Thu Oct 30 17:02:30 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id RAA09682
for <maillist@candle.pha.pa.us>; Thu, 30 Oct 1997 17:02:28 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id QAA20688; Thu, 30 Oct 1997 16:58:40 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 30 Oct 1997 16:58:24 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id QAA20615 for pgsql-hackers-outgoing; Thu, 30 Oct 1997 16:58:17 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id QAA20495 for <hackers@postgreSQL.org>; Thu, 30 Oct 1997 16:57:54 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id QAA07726
for hackers@postgreSQL.org; Thu, 30 Oct 1997 16:50:29 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Thu, 30 Oct 1997 16:50:29 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
The only thing I have to add to what I had written earlier is that I
think it is best to have these subqueries executed as early in query
execution as possible.
Every piece of the backend: parser, optimizer, executor, is designed to
work on a single query. The earlier we can split up the queries, the
better those pieces will work at doing their job. You want to be able
to use the parser and optimizer on each part of the query separately, if
you can.
Forwarded message:
> I have done some thinking about subselects. There are basically two
> issues:
>
> Does the query return one row or several rows? This can be
> determined by seeing if the user uses equals on 'IN' to join the
> subquery.
>
> Is the query correlated, meaning "Does the subquery reference
> values from the outer query?"
>
> (We already have the third type of subquery, the INSERT...SELECT query.)
>
> So we have these four combinations:
>
> 1) one row, no correlation
> 2) multiple rows, no correlation
> 3) one row, correlated
> 4) multiple rows, correlated
>
>
> With #1, we can execute the subquery, get the value, replace the
> subquery with the constant returned from the subquery, and execute the
> outer query.
>
> With #2, we can execute the subquery and put the result into a temporary
> table. We then rewrite the outer query to access the temporary table
> and replace the subquery with the column name from the temporary table.
> We probabally put an index on the temp. table, which has only one
> column, because a subquery can only return one column. We remove the
> temp. table after query execution.
>
> With #3 and #4, we potentially need to execute the subquery for every
> row returned by the outer query. Performance would be horrible for
> anything but the smallest query. Another way to handle this is to
> execute the subquery WITHOUT using any of the outer-query columns to
> restrict the WHERE clause, and add those columns used to join the outer
> variables into the target list of the subquery. So for query:
>
> select t1.name
> from tab t1
> where t1.age = (select max(t2.age)
> from tab2
> where tab2.name = t1.name)
>
> Execute the subquery and put it in a temporary table:
>
> select t2.name, max(t2.age)
> into table temp999
> from tab2
> where tab2.name = t1.name
>
> create index i_temp999 on temp999 (name)
>
> Then re-write the outer query:
>
> select t1.name
> from tab t1, temp999
> where t1.age = temp999.age and
> t1.name = temp999.name
>
> The only problem here is that the subselect is running for all entries
> in tab2, even if the outer query is only going to need a few rows.
> Determining whether to execute the subquery each time, or create a temp.
> table is often difficult to determine. Even some non-correlated
> subqueries are better to execute for each row rather the pre-execute the
> entire subquery, expecially if the outer query returns few rows.
>
> One requirement to handle these issues is better column statistics,
> which I am working on.
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Fri Oct 31 22:30:58 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id WAA15643
for <maillist@candle.pha.pa.us>; Fri, 31 Oct 1997 22:30:56 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id WAA24379 for <maillist@candle.pha.pa.us>; Fri, 31 Oct 1997 22:06:08 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id WAA15503; Fri, 31 Oct 1997 22:03:40 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 31 Oct 1997 22:01:38 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id WAA14136 for pgsql-hackers-outgoing; Fri, 31 Oct 1997 22:01:29 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id WAA13866 for <hackers@postgreSQL.org>; Fri, 31 Oct 1997 22:00:53 -0500 (EST)
In-Reply-To: <199710302150.QAA07726@candle.pha.pa.us> from "Bruce Momjian" at Oct 30, 97 04:50:29 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
One more issue I thought of. You can have multiple subselects in a
single query, and subselects can have their own subselects.
This makes it particularly important that we define a system that always
is able to process the subselect BEFORE the upper select. This will
allow use to handle all these cases without limitations.
>
> The only thing I have to add to what I had written earlier is that I
> think it is best to have these subqueries executed as early in query
> execution as possible.
>
> Every piece of the backend: parser, optimizer, executor, is designed to
> work on a single query. The earlier we can split up the queries, the
> better those pieces will work at doing their job. You want to be able
> to use the parser and optimizer on each part of the query separately, if
> you can.
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From hannu@trust.ee Sun Nov 2 10:33:33 1997
Received: from sid.trust.ee (sid.trust.ee [194.204.23.180])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA27619
for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 10:32:04 -0500 (EST)
Received: from sid.trust.ee (wink.trust.ee [194.204.23.184])
by sid.trust.ee (8.8.5/8.8.5) with ESMTP id RAA02233;
Sun, 2 Nov 1997 17:30:11 +0200
Message-ID: <345C9BFD.986C68AA@sid.trust.ee>
Date: Sun, 02 Nov 1997 17:27:57 +0200
From: Hannu Krosing <hannu@trust.ee>
X-Mailer: Mozilla 4.02 [en] (Win95; I)
MIME-Version: 1.0
To: hackers-digest@postgresql.org
CC: maillist@candle.pha.pa.us
Subject: Re: [HACKERS] subselects
References: <199711010401.XAA09216@hub.org>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Status: OR
> Date: Fri, 31 Oct 1997 21:37:06 +1900 (EST)
> From: Bruce Momjian <maillist@candle.pha.pa.us>
> Subject: Re: [HACKERS] subselects
>
> One more issue I thought of. You can have multiple subselects in a
> single query, and subselects can have their own subselects.
>
> This makes it particularly important that we define a system that always
> is able to process the subselect BEFORE the upper select. This will
> allow use to handle all these cases without limitations.
This would severely limit what subselects can be used for as you can't useany of the fields in the upper select in a
search criteria for the subselect,
for example you can't do
update parts p1
set parts.current_id = (
select new_id
from parts p2
where p1.old_id = p2.new_id);or
select id, price, (select sum(price) from parts p2 where p1.id=p2.id) as totalprice
from parts p1;
there may be of course ways to rewrite these queries (which the optimiser should do
if it can) but IMHO, these kinds of subselects should still be allowed
> > The only thing I have to add to what I had written earlier is that I
> > think it is best to have these subqueries executed as early in query
> > execution as possible.
> >
> > Every piece of the backend: parser, optimizer, executor, is designed to
> > work on a single query. The earlier we can split up the queries, the
> > better those pieces will work at doing their job. You want to be able
> > to use the parser and optimizer on each part of the query separately, if
> > you can.
> >
>
Hannu
From vadim@sable.krasnoyarsk.su Sun Nov 2 21:30:59 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id VAA14831
for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 21:30:57 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id VAA19683 for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 21:20:13 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id JAA17259; Mon, 3 Nov 1997 09:22:38 +0700 (KRS)
> > > One more issue I thought of. You can have multiple subselects in a
> > > single query, and subselects can have their own subselects.
> > >
> > > This makes it particularly important that we define a system that always
> > > is able to process the subselect BEFORE the upper select. This will
> > > allow use to handle all these cases without limitations.
> >
> > This would severely limit what subselects can be used for as you can't useany of the fields in the upper select in a
> > search criteria for the subselect,
> > for example you can't do
> >
> > update parts p1
> > set parts.current_id = (
> > select new_id
> > from parts p2
> > where p1.old_id = p2.new_id);or
> >
> > select id, price, (select sum(price) from parts p2 where p1.id=p2.id) as totalprice
> > from parts p1;
> >
> > there may be of course ways to rewrite these queries (which the optimiser should do
> > if it can) but IMHO, these kinds of subselects should still be allowed
>
> I hadn't even gotten to this point yet, but it is a good thing to keep
> in mind.
>
> In these cases, as in correlated subqueries in the where clause, we will
> create a temporary table, and add the proper join fields and tables to
> the clauses. Our version of UPDATE accepts a FROM section, and we will
> certainly use this for this purpose.
We can't replace subselect with join if there is aggregate
in subselect.
Actually, I don't see any problems if we going to process subselect
like sql-funcs: non-correlated subselects can be emulated by
funcs without args, for correlated subselects parser (analyze.c)
has to change all upper query references to $1, $2,...
Vadim
From vadim@sable.krasnoyarsk.su Mon Nov 3 06:07:12 1997
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id GAA27433
for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 06:07:03 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id SAA18519; Mon, 3 Nov 1997 18:09:44 +0700 (KRS)
first tries to sort sizeof(table_a) * sizeof(table_b) tuples...
For tables big and small with 100 000 and 1000 tuples
select max(x*y), x from big, small group by x
"ate" all free 140M in my file system after 20 minutes (just for
sorting - nothing more) and was killed...
select x from big where x = cor(x);
(cor(int4) is 'select max($1*y) from small') takes 20 minutes -
this is bad too.
> >
> > Actually, I don't see any problems if we going to process subselect
> > like sql-funcs: non-correlated subselects can be emulated by
> > funcs without args, for correlated subselects parser (analyze.c)
> > has to change all upper query references to $1, $2,...
>
> Yes, logically, they are SQL functions, but aren't we going to see
> terrible performance in such circumstances. My experience is that when
^^^^^^^^^^^^^^^^^^^^
You're right.
> people are given subselects, they start to do huge jobs with them.
>
> In fact, the final solution may be to have both methods available, and
> switch between them depending on the size of the query sets. Each
> method has its advantages. The function example lets the outside query
> be executed, and only calls the subquery when needed.
>
> For large tables where the subselect is small and is the entire WHERE
> restriction, the SQL function gets call much too often. A simple join
> of the subquery result and the large table would be much better. This
> method also allows for sort/merge join of the subquery results, and
> index use.
...keep thinking...
Vadim
From owner-pgsql-hackers@hub.org Mon Nov 3 11:01:01 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id LAA03633
for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 11:00:59 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id KAA12174 for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 10:49:42 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id KAA26203; Mon, 3 Nov 1997 10:33:32 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 03 Nov 1997 10:31:43 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id KAA25514 for pgsql-hackers-outgoing; Mon, 3 Nov 1997 10:31:36 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id KAA25449 for <hackers@postgreSQL.org>; Mon, 3 Nov 1997 10:31:23 -0500 (EST)
> first tries to sort sizeof(table_a) * sizeof(table_b) tuples...
> For tables big and small with 100 000 and 1000 tuples
>
> select max(x*y), x from big, small group by x
>
> "ate" all free 140M in my file system after 20 minutes (just for
> sorting - nothing more) and was killed...
>
> select x from big where x = cor(x);
> (cor(int4) is 'select max($1*y) from small') takes 20 minutes -
> this is bad too.
Again, my feeling is that in cases where the temp table would bomb, the
SQL function will be so slow that neither will be acceptable.
>
> > >
> > > Actually, I don't see any problems if we going to process subselect
> > > like sql-funcs: non-correlated subselects can be emulated by
> > > funcs without args, for correlated subselects parser (analyze.c)
> > > has to change all upper query references to $1, $2,...
> >
> > Yes, logically, they are SQL functions, but aren't we going to see
> > terrible performance in such circumstances. My experience is that when
> ^^^^^^^^^^^^^^^^^^^^
> You're right.
>
> > people are given subselects, they start to do huge jobs with them.
> >
> > In fact, the final solution may be to have both methods available, and
> > switch between them depending on the size of the query sets. Each
> > method has its advantages. The function example lets the outside query
> > be executed, and only calls the subquery when needed.
> >
> > For large tables where the subselect is small and is the entire WHERE
> > restriction, the SQL function gets call much too often. A simple join
> > of the subquery result and the large table would be much better. This
> > method also allows for sort/merge join of the subquery results, and
> > index use.
>
> ...keep thinking...
>
> Vadim
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Thu Nov 20 00:09:18 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA05239
for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 00:09:11 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id XAA13776; Wed, 19 Nov 1997 23:59:53 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Wed, 19 Nov 1997 23:58:49 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id XAA13599 for pgsql-hackers-outgoing; Wed, 19 Nov 1997 23:58:43 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id XAA13512 for <hackers@postgreSQL.org>; Wed, 19 Nov 1997 23:58:16 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id XAA03103
for hackers@postgreSQL.org; Wed, 19 Nov 1997 23:57:44 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Wed, 19 Nov 1997 23:57:44 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
I am going to overhaul all the /parser files, and I may give subselects
a try while I am in there. This is where it going to have to be done.
Two things I think I need are:
temp tables that go away at the end of a statement, so if the
query elog's out, the temp file gets destroyed
how do I implement "not in":
select * from a where x not in (select y from b)
Using <> is not going to work because that returns multiple copies of a,
one for every one that doesn't equal. It is like we need not equals,
but don't return multiple rows.
Any ideas?
--
Bruce Momjian
maillist@candle.pha.pa.us
From lockhart@alumni.caltech.edu Thu Nov 20 10:00:59 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA22019
for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 10:00:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id JAA21662 for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 09:52:55 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id GAA22754;
> a try while I am in there. This is where it going to have to be done.
A first cut at the subselect syntax is already in gram.y. I'm sure that the
e-mail you had sent which collected several items regarding subselects
covers some of this topic. I've been thinking about subselects also, and
had thought that there must be some existing mechanisms in the backend
which can be used to help implement subselects. It seems to me that UNION
might be a good thing to implement first, because it has a fairly
well-defined set of behaviors:
select a union select b;
chooses elements from a and from b and then sorts/uniques the result.
select a union all select b;
chooses elements from a, sorts/uniques, and then adds all elements from b.
select a union select b union all select c;
evaluates left to right, and first evaluates a union b, sorts/uniques, and
then evaluates
(result) union all select c;
There are several types of subselects. Examples of some are:
1) select a.f from a union select b.f from b order by 1;
Needs temporary table(s), optional sort/unique, final order by.
2) select a.f from a where a.f in (select b.f from b);
Needs temporary table(s). "in" can be first implemented by count(*) > 0 but
would be better performance to have the backend return after the first
match.
3) select a.f from a where exists (select b.f from b where b.f = a);
Need to do the select and do a subselect on _each_ of the returned values?
Again could use count(*) to help implement.
This brings up the point that perhaps the backend needs a row-counting
atomic operation and count(*) could be re-implemented using that. At the
moment count(*) is transformed to a select of OID columns and does not
quite work on table joins.
I would think that outer joins could use some of these support routines
also.
- Tom
> Two things I think I need are:
>
> temp tables that go away at the end of a statement, so if the
> query elog's out, the temp file gets destroyed
>
> how do I implement "not in":
>
> select * from a where x not in (select y from b)
>
> Using <> is not going to work because that returns multiple copies of a,
> one for every one that doesn't equal. It is like we need not equals,
> but don't return multiple rows.
>
> Any ideas?
>
> --
> Bruce Momjian
> maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Mon Dec 22 00:49:03 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA13311
for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 00:49:01 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id AAA11930; Mon, 22 Dec 1997 00:45:41 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 22 Dec 1997 00:45:17 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id AAA11756 for pgsql-hackers-outgoing; Mon, 22 Dec 1997 00:45:14 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id AAA11624 for <hackers@postgreSQL.org>; Mon, 22 Dec 1997 00:44:57 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id AAA11605
for hackers@postgreSQL.org; Mon, 22 Dec 1997 00:45:23 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Mon, 22 Dec 1997 00:45:23 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
OK, a few questions:
Should we use sortmerge, so we can use our psort as temp tables,
or do we use hashunique?
How do we pass the query to the optimizer? How do we represent
the range table for each, and the links between them in correlated
subqueries?
I have to think about this. Comments are welcome.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Mon Dec 22 02:01:27 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id CAA20608
for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 02:01:25 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA25136 for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 01:37:29 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA25289; Mon, 22 Dec 1997 01:31:18 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 22 Dec 1997 01:30:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA23854 for pgsql-hackers-outgoing; Mon, 22 Dec 1997 01:30:35 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id BAA22847 for <hackers@postgreSQL.org>; Mon, 22 Dec 1997 01:30:15 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id BAA17354
for hackers@postgreSQL.org; Mon, 22 Dec 1997 01:05:04 -0500 (EST)
> > Should we use sortmerge, so we can use our psort as temp tables,
> > or do we use hashunique?
> >
> > How do we pass the query to the optimizer? How do we represent
> > the range table for each, and the links between them in correlated
> > subqueries?
> >
> > I have to think about this. Comments are welcome.
>
> One more thing. I guess I am seeing subselects as a different thing
> that temp tables. I can see people wanting to put indexes on their temp
> tables, so I think they will need more system catalog support. For
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What's the difference between temp tables and temp indices ?
Both of them are handled via catalog cache...
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 3 04:01:00 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA28565
for <maillist@candle.pha.pa.us>; Sat, 3 Jan 1998 04:00:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id DAA19242 for <maillist@candle.pha.pa.us>; Sat, 3 Jan 1998 03:47:07 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA21017;
> With UNIONs done, how are things going with you on subselects? UNIONs
> are much easier that subselects.
>
> I am stumped on how to record the subselect query information in the
> parser and stuff.
And I'm too. We definitely need in EXISTS node and may be in IN one.
Also, we have to support ANY and ALL modifiers of comparison operators
(it would be nice to support ANY and ALL for all operators returning
bool: >, =, ..., like, ~ and so on). Note, that IN is the same as
= ANY (NOT IN ==> <> ALL) assuming that '=' means EQUAL for all data types,
and so, we could avoid IN node, but I'm not sure that I like such
assumption: postgres is OO-like system allowing operators to be overriden
and so, '=' can, in theory, mean not EQUAL but something else (someday
we could allow to specify "meaning" of operator in CREATE OPERATOR) -
in short, I would like IN node.
Also, I would suggest nodes for ANY and ALL.
(I need in few days to think more about recording of this stuff...)
>
> Please let me know what I can do to help, if anything.
Thanks. As I remember, Tom also wished to work here. Tom ?
Bye,
Vadim
P.S. I'll be "on-line" Jan 5.
From owner-pgsql-hackers@hub.org Mon Jan 5 07:30:51 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id HAA05466
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 07:30:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id HAA04700; Mon, 5 Jan 1998 07:22:06 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 07:21:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id HAA02846 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 07:21:35 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.5/8.7.5) with ESMTP id HAA00903 for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 07:20:57 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id TAA24278;
> I was thinking about subselects, and how to attach the two queries.
>
> What if the subquery makes a range table entry in the outer query, and
> the query is set up like the UNION queries where we put the scans in a
> row, but in the case we put them over/under each other.
>
> And we push a temp table into the catalog cache that represents the
> result of the subquery, then we could join to it in the outer query as
> though it was a real table.
>
> Also, can't we do the correlated subqueries by adding the proper
> target/output columns to the subquery, and have the outer query
> reference those columns in the subquery range table entry.
Yes, this is a way to handle subqueries by joining to temp table.
After getting plan we could change temp table access path to
node material. On the other hand, it could be useful to let optimizer
know about cost of temp table creation (have to think more about it)...
Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
is one example of this - joining by <> will give us invalid results.
Setting special NOT EQUAL flag is not enough: subquery plan must be
always inner one in this case. The same for handling ALL modifier.
Note, that we generaly can't use aggregates here: we can't add MAX to
subquery in the case of > ALL (subquery), because of > ALL should return FALSE
if subquery returns NULL(s) but aggregates don't take NULLs into account.
>
> Maybe I can write up a sample of this? Vadim, would this help? Is this
> the point we are stuck at?
Personally, I was stuck by holydays -:)
Now I can spend ~ 8 hours ~ each day for development...
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 10:45:30 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA10769
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 10:45:28 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id KAA17823; Mon, 5 Jan 1998 10:32:00 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 10:31:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id KAA17757 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 10:31:38 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id KAA17727 for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 10:31:06 -0500 (EST)
In-Reply-To: <34B0D3AF.F31338B3@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 5, 98 07:35:59 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> Yes, this is a way to handle subqueries by joining to temp table.
> After getting plan we could change temp table access path to
> node material. On the other hand, it could be useful to let optimizer
> know about cost of temp table creation (have to think more about it)...
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
> Setting special NOT EQUAL flag is not enough: subquery plan must be
> always inner one in this case. The same for handling ALL modifier.
> Note, that we generaly can't use aggregates here: we can't add MAX to
> subquery in the case of > ALL (subquery), because of > ALL should return FALSE
> if subquery returns NULL(s) but aggregates don't take NULLs into account.
OK, here are my ideas. First, I think you have to handle subselects in
the outer node because a subquery could have its own subquery. Also, we
now have a field in Aggreg to all us to 'usenulls'.
OK, here it is. I recommend we pass the outer and subquery through
the parser and optimizer separately.
We parse the subquery first. If the subquery is not correlated, it
should parse fine. If it is correlated, any columns we find in the
subquery that are not already in the FROM list, we add the table to the
subquery FROM list, and add the referenced column to the target list of
the subquery.
When we are finished parsing the subquery, we create a catalog cache
entry for it called 'sub1' and make its fields match the target
list of the subquery.
In the outer query, we add 'sub1' to its target list, and change
the subquery reference to point to the new range table. We also add
WHERE clauses to do any correlated joins.
Here is a simple example:
select *
from taba
where col1 = (select col2
from tabb)
This is not correlated, and the subquery parser easily. We create a
'sub1' catalog cache entry, and add 'sub1' to the outer query FROM
clause. We also replace 'col1 = (subquery)' with 'col1 = sub1.col2'.
Here is a more complex correlated subquery:
select *
from taba
where col1 = (select col2
from tabb
where taba.col3 = tabb.col4)
Here we must add 'taba' to the subquery's FROM list, and add col3 to the
target list of the subquery. After we parse the subquery, add 'sub1' to
the FROM list of the outer query, change 'col1 = (subquery)' to 'col1 =
sub1.col2', and add to the outer WHERE clause 'AND taba.col3 = sub1.col3'.
THe optimizer will do the correlation for us.
In the optimizer, we can parse the subquery first, then the outer query,
and then replace all 'sub1' references in the outer query to use the
subquery plan.
I realize making merging the two plans and doing IN and NOT IN is the
real challenge, but I hoped this would give us a start.
What do you think?
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Mon Jan 5 15:02:46 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id PAA28690
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 15:02:44 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id OAA08811 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 14:28:43 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id CAA24904;
> > always inner one in this case. The same for handling ALL modifier.
> > Note, that we generaly can't use aggregates here: we can't add MAX to
> > subquery in the case of > ALL (subquery), because of > ALL should return FALSE
> > if subquery returns NULL(s) but aggregates don't take NULLs into account.
>
> OK, here are my ideas. First, I think you have to handle subselects in
> the outer node because a subquery could have its own subquery. Also, we
I hope that this is no matter: if results of subquery (with/without sub-subqueries)
will go into temp table then this table will be re-scanned for each outer tuple.
> now have a field in Aggreg to all us to 'usenulls'.
^^^^^^^^
This can't help:
vac=> select * from x;
y
-
1
2
3
<<< this is NULL
(4 rows)
vac=> select max(y) from x;
max
---
3
==> we can't replace
select * from A where A.a > ALL (select y from x);
^^^^^^^^^^^^^^^
(NULL will be returned and so A.a > ALL is FALSE - this is what
Sybase does, is it right ?)
with
select * from A where A.a > (select max(y) from x);
^^^^^^^^^^^^^^^^^^^^
just because of we lose knowledge about NULLs here.
Also, I would like to handle ANY and ALL modifiers for all bool
operators, either built-in or user-defined, for all data types -
isn't PostgreSQL OO-like RDBMS -:)
> OK, here it is. I recommend we pass the outer and subquery through
> the parser and optimizer separately.
I don't like this. I would like to get parse-tree from parser for
entire query and let optimizer (on upper level) decide how to rewrite
parse-tree and what plans to produce and how these plans should be
merged. Note, that I don't object your methods below, but only where
to place handling of this. I don't understand why should we add
new part to the system which will do optimizer' work (parse-tree -->
execution plan) and deal with optimizer nodes. Imho, upper optimizer
level is nice place to do this.
>
> We parse the subquery first. If the subquery is not correlated, it
> should parse fine. If it is correlated, any columns we find in the
> subquery that are not already in the FROM list, we add the table to the
> subquery FROM list, and add the referenced column to the target list of
> the subquery.
>
> When we are finished parsing the subquery, we create a catalog cache
> entry for it called 'sub1' and make its fields match the target
> list of the subquery.
>
> In the outer query, we add 'sub1' to its target list, and change
> the subquery reference to point to the new range table. We also add
> WHERE clauses to do any correlated joins.
...
> Here is a more complex correlated subquery:
>
> select *
> from taba
> where col1 = (select col2
> from tabb
> where taba.col3 = tabb.col4)
>
> Here we must add 'taba' to the subquery's FROM list, and add col3 to the
> target list of the subquery. After we parse the subquery, add 'sub1' to
> the FROM list of the outer query, change 'col1 = (subquery)' to 'col1 =
> sub1.col2', and add to the outer WHERE clause 'AND taba.col3 = sub1.col3'.
> THe optimizer will do the correlation for us.
>
> In the optimizer, we can parse the subquery first, then the outer query,
> and then replace all 'sub1' references in the outer query to use the
> subquery plan.
>
> I realize making merging the two plans and doing IN and NOT IN is the
^^^^^^^^^^^^^^^^^^^^^
This is very easy to do! As I already said we have just change sub1
access path (SeqScan of sub1) with SeqScan of Material node with
subquery plan.
> real challenge, but I hoped this would give us a start.
Decision about how to record subquery stuff in to parse-tree
would be very good start -:)
BTW, note that for _expression_ subqueries (which are introduced without
IN, EXISTS, ALL, ANY - this follows Sybase' naming) - as in your examples -
we have to check that subquery returns single tuple...
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 20:31:03 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id UAA06836
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:31:01 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id TAA29980 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 19:56:05 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28044; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:16 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27203 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:02 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27049 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:30 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09337
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:31:04 -0500 (EST)
One thought to follow this way: RULEs (and so - VIEWs) are handled by using
Query - how else can we implement VIEWs on selects with subqueries ?
BTW, is
select * from A where (select TRUE from B);
valid syntax ?
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 5 18:00:57 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id SAA03296
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:00:55 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id RAA20716 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 17:22:21 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id FAA25094;
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
>
> What is you approach towards this problem?
Actually, this is problem of ALL modifier (NOT IN is _not_equal_ ALL)
and so, we have to have not just NOT EQUAL flag but some ALL node
with modified operator.
After that, one way is put subquery into inner plan of an join node
to be sure that for an outer tuple all corresponding subquery tuples
will be tested with modified operator (this will require either
changing code of all join nodes or addition of new plan type - we'll see)
and another way is ... suggested by you:
> I got an idea that one could reverse the order,
> that is execute the outer first into a temptable
> and delete from that according to the result of the
> subquery and then return it.
> Probably this is too raw and slow. ;-)
This will be faster in some cases (when subquery returns many results
and there are "not so many" results from outer query) - thanks for idea!
>
> Personally, I was stuck by holydays -:)
> Now I can spend ~ 8 hours ~ each day for development...
>
> Oh, isn't it christmas eve right now in Russia?
Due to historic reasons New Year is mu-u-u-uch popular
holiday in Russia -:)
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 19:32:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id TAA05070
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 19:32:57 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id SAA26847 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:59:43 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28045; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:40 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27280 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:25 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27030 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:25 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09438
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:35:43 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id FAA25094;
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
>
> What is you approach towards this problem?
Actually, this is problem of ALL modifier (NOT IN is _not_equal_ ALL)
and so, we have to have not just NOT EQUAL flag but some ALL node
with modified operator.
After that, one way is put subquery into inner plan of an join node
to be sure that for an outer tuple all corresponding subquery tuples
will be tested with modified operator (this will require either
changing code of all join nodes or addition of new plan type - we'll see)
and another way is ... suggested by you:
> I got an idea that one could reverse the order,
> that is execute the outer first into a temptable
> and delete from that according to the result of the
> subquery and then return it.
> Probably this is too raw and slow. ;-)
This will be faster in some cases (when subquery returns many results
and there are "not so many" results from outer query) - thanks for idea!
>
> Personally, I was stuck by holydays -:)
> Now I can spend ~ 8 hours ~ each day for development...
>
> Oh, isn't it christmas eve right now in Russia?
Due to historic reasons New Year is mu-u-u-uch popular
holiday in Russia -:)
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 5 18:00:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id SAA03300
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:00:57 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id RAA21652 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 17:42:15 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id GAA25129;
> > and SubSelect (Query) here (as possible case).
> >
> > One thought to follow this way: RULEs (and so - VIEWs) are handled by using
> > Query - how else can we implement VIEWs on selects with subqueries ?
>
> Views are stored as nodeout structures, and are merged into the query's
> from list, target list, and where clause. I am working out
> readfunc,outfunc now to make sure they are up-to-date with all the
> current fields.
Nice! This stuff was out-of-date for too long time.
> > BTW, is
> >
> > select * from A where (select TRUE from B);
> >
> > valid syntax ?
>
> I don't think so.
And so, *rexpr can be of Query type only for oper "in" OP, IN, NOT IN,
ANY, ALL, EXISTS - well.
(Time to sleep -:)
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 20:31:08 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id UAA06842
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:31:06 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id UAA00621 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:03:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28043; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:38 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27270 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:22 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27141 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:50 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09919
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:54:47 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id GAA25129;
> > and SubSelect (Query) here (as possible case).
> >
> > One thought to follow this way: RULEs (and so - VIEWs) are handled by using
> > Query - how else can we implement VIEWs on selects with subqueries ?
>
> Views are stored as nodeout structures, and are merged into the query's
> from list, target list, and where clause. I am working out
> readfunc,outfunc now to make sure they are up-to-date with all the
> current fields.
Nice! This stuff was out-of-date for too long time.
> > BTW, is
> >
> > select * from A where (select TRUE from B);
> >
> > valid syntax ?
>
> I don't think so.
And so, *rexpr can be of Query type only for oper "in" OP, IN, NOT IN,
ANY, ALL, EXISTS - well.
(Time to sleep -:)
Vadim
From owner-pgsql-hackers@hub.org Thu Jan 8 23:10:50 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id XAA09707
for <maillist@candle.pha.pa.us>; Thu, 8 Jan 1998 23:10:48 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id XAA19334 for <maillist@candle.pha.pa.us>; Thu, 8 Jan 1998 23:08:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id XAA14375; Thu, 8 Jan 1998 23:03:29 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 08 Jan 1998 23:03:10 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id XAA14345 for pgsql-hackers-outgoing; Thu, 8 Jan 1998 23:03:06 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id XAA14008 for <hackers@postgreSQL.org>; Thu, 8 Jan 1998 23:00:50 -0500 (EST)
Vadim, I know you are still thinking about subselects, but I have some
more clarification that may help.
We have to add phantom range table entries to correlated subselects so
they will pass the parser. We might as well add those fields to the
target list of the subquery at the same time:
select *
from taba
where col1 = (select col2
from tabb
where taba.col3 = tabb.col4)
becomes:
select *
from taba
where col1 = (select col2, tabb.col4 <---
from tabb, taba <---
where taba.col3 = tabb.col4)
We add a field to TargetEntry and RangeTblEntry to mark the fact that it
was entered as a correlation entry:
bool isCorrelated;
Second, we need to hook the subselect to the main query. I recommend we
add two fields to Query for this:
Query *parentQuery;
List *subqueries;
The parentQuery pointer is used to resolve field names in the correlated
subquery.
select *
from taba
where col1 = (select col2, tabb.col4 <---
from tabb, taba <---
where taba.col3 = tabb.col4)
In the query above, the subquery can be easily parsed, and we add the
subquery to the parsent's parentQuery list.
In the parent query, to parse the WHERE clause, we create a new operator
type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
right side is an index to a slot in the subqueries List.
We can then do the rest in the upper optimizer.
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Fri Jan 9 10:01:01 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA27305
for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 10:00:59 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id JAA21583 for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 09:52:17 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id WAA01623;
> Vadim, I know you are still thinking about subselects, but I have some
> more clarification that may help.
>
> We have to add phantom range table entries to correlated subselects so
> they will pass the parser. We might as well add those fields to the
> target list of the subquery at the same time:
>
> select *
> from taba
> where col1 = (select col2
> from tabb
> where taba.col3 = tabb.col4)
>
> becomes:
>
> select *
> from taba
> where col1 = (select col2, tabb.col4 <---
> from tabb, taba <---
> where taba.col3 = tabb.col4)
>
> We add a field to TargetEntry and RangeTblEntry to mark the fact that it
> was entered as a correlation entry:
>
> bool isCorrelated;
No, I don't like to add anything in parser. Example:
select *
from tabA
where col1 = (select col2
from tabB
where tabA.col3 = tabB.col4
and exists (select *
from tabC
where tabB.colX = tabC.colX and
tabC.colY = tabA.col2)
)
: a column of tabA is referenced in sub-subselect
(is it allowable by standards ?) - in this case it's better
to don't add tabA to 1st subselect but add tabA to second one
and change tabA.col3 in 1st to reference col3 in 2nd subquery temp table -
this gives us 2-tables join in 1st subquery instead of 3-tables join.
(And I'm still not sure that using temp tables is best of what can be
done in all cases...)
Instead of using isCorrelated in TE & RTE we can add
Index varlevel;
to Var node to reflect (sub)query from where this Var is come
(where is range table to find var's relation using varno). Upmost query
will have varlevel = 0, all its (dirrect) children - varlevel = 1 and so on.
^^^ ^^^^^^^^^^^^
(I don't see problems with distinguishing Vars of different children
on the same level...)
>
> Second, we need to hook the subselect to the main query. I recommend we
> add two fields to Query for this:
>
> Query *parentQuery;
> List *subqueries;
Agreed. And maybe Index queryLevel.
> In the parent query, to parse the WHERE clause, we create a new operator
> type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
^^^^^^^^^^^^^^^^^^
No. We have to handle (a,b,c) OP (select x, y, z ...) and
'_a_constant_' OP (select ...) - I don't know is last in standards,
Sybase has this.
Well,
typedef enum OpType
{
OP_EXPR, FUNC_EXPR, OR_EXPR, AND_EXPR, NOT_EXPR
+ OP_EXISTS, OP_ALL, OP_ANY
} OpType;
typedef struct Expr
{
NodeTag type;
Oid typeOid; /* oid of the type of this expr */
OpType opType; /* type of the op */
Node *oper; /* could be Oper or Func */
List *args; /* list of argument nodes */
} Expr;
OP_EXISTS: oper is NULL, lfirst(args) is SubSelect (index in subqueries
List, following your suggestion)
OP_ALL, OP_ANY:
oper is List of Oper nodes. We need in list because of data types of
a, b, c (above) can be different and so Oper nodes will be different too.
lfirst(args) is List of expression nodes (Const, Var, Func ?, a + b ?) -
left side of subquery' operator.
lsecond(args) is SubSelect.
Note, that there are no OP_IN, OP_NOTIN in OpType-s for Expr. We need in
IN, NOTIN in A_Expr (parser node), but both of them have to be transferred
by parser into corresponding ANY and ALL. At the moment we can do:
IN --> = ANY, NOT IN --> <> ALL
but this will be "known bug": this breaks OO-nature of Postgres, because of
operators can be overrided and '=' can mean s o m e t h i n g (not equality).
Example: box data type. For boxes, = means equality of _areas_ and =~
means that boxes are the same ==> =~ ANY should be used for IN.
> right side is an index to a slot in the subqueries List.
Vadim
From owner-pgsql-hackers@hub.org Fri Jan 9 17:44:04 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id RAA24779
for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 17:44:01 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id RAA20728; Fri, 9 Jan 1998 17:32:34 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 09 Jan 1998 17:32:19 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id RAA20503 for pgsql-hackers-outgoing; Fri, 9 Jan 1998 17:32:15 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id RAA20008 for <hackers@postgresql.org>; Fri, 9 Jan 1998 17:31:24 -0500 (EST)
easy extensibility of Postgres, it replaces the PostQuel query language with an
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
extended subset of SQL.
^^^^^^^^^^^^^^^^^^^^^^
Should we say users that subselect will work for standard data types only ?
I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
Is there difference between handling = ANY and ~ ANY ? I don't see any.
Currently we can't get IN working properly for boxes (and may be for others too)
and I don't like to try to resolve these problems now, but hope that someday
we'll be able to do this. At the moment - just convert IN into = ANY and
NOT IN into <> ALL in parser.
(BTW, do you know how DISTINCT is implemented ? It doesn't use = but
use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
> >
> > > right side is an index to a slot in the subqueries List.
>
> I guess the question is what can we have by February 1?
>
> I have been reading some postings, and it seems to me that subselects
> are the litmus test for many evaluators when deciding if a database
> engine is full-featured.
>
> Sorry to be so straightforward, but I want to keep hashing this around
> until we get a conclusion, so coding can start.
>
> My suggestions have been, I believe, trying to get subselects working
> with the fullest functionality by adding the least amount of code, and
> keeping the logic clean.
>
> Have you checked out the UNION code? It is very small, but it works. I
> think it could make a good sample for subselects.
There is big difference between subqueries and queries in UNION -
there are not dependences between UNION queries.
Ok, opened issues:
1. Is using upper query' vars in all subquery levels in standard ?
2. Is (a, b, c) OP (subselect) in standard ?
3. What types of expressions (Var, Const, ...) are allowed on the left
side of operator with subquery on the right ?
4. What types of operators should we support (=, >, ..., like, ~, ...) ?
(My vote for all boolean operators).
And - did we get consensus on presentation subqueries stuff in Query,
Expr and Var ?
I would like to have something done in parser near Jan 17 to get
subqueries working by Feb 1. I vote for support of all standard
things (1. - 3.) in parser right now - if there will be no time
to implement something like (a, b, c) then optimizer will call
elog(WARN) (oh, sorry, - elog(ERROR)).
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 10 12:31:05 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id MAA29045
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:31:01 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id MAA23364 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:22:30 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id AAA05725;
> Should we use sortmerge, so we can use our psort as temp tables,
> or do we use hashunique?
>
> How do we pass the query to the optimizer? How do we represent
> the range table for each, and the links between them in correlated
> subqueries?
My suggestion is just use varlevel in Var and don't put upper query'
relations into subquery range table.
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 10 13:01:00 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id NAA29357
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:00:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id MAA24030 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:40:02 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id AAA05741;
> > Should we use sortmerge, so we can use our psort as temp tables,
> > or do we use hashunique?
> >
> > How do we pass the query to the optimizer? How do we represent
> > the range table for each, and the links between them in correlated
> > subqueries?
>
> My suggestion is just use varlevel in Var and don't put upper query'
> relations into subquery range table.
Hmm... Sorry, it seems that I did reply to very old message - forget it.
Vadim
From lockhart@alumni.caltech.edu Sat Jan 10 13:30:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id NAA29664
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:30:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id NAA25109 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:05:09 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id SAA03623;
> easy extensibility of Postgres, it replaces the PostQuel query language with an
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> extended subset of SQL.
> ^^^^^^^^^^^^^^^^^^^^^^
>
> Should we say users that subselect will work for standard data types only ?
> I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
> Is there difference between handling = ANY and ~ ANY ? I don't see any.
> Currently we can't get IN working properly for boxes (and may be for others too)
> and I don't like to try to resolve these problems now, but hope that someday
> we'll be able to do this. At the moment - just convert IN into = ANY and
> NOT IN into <> ALL in parser.
>
> (BTW, do you know how DISTINCT is implemented ? It doesn't use = but
> use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
?? I didn't know that. Wouldn't we want it to eventually use "=" through a sorted
list? That would give more consistant behavior...
> > I have been reading some postings, and it seems to me that subselects
> > are the litmus test for many evaluators when deciding if a database
> > engine is full-featured.
> >
> > Sorry to be so straightforward, but I want to keep hashing this around
> > until we get a conclusion, so coding can start.
> >
> > My suggestions have been, I believe, trying to get subselects working
> > with the fullest functionality by adding the least amount of code, and
> > keeping the logic clean.
> >
> > Have you checked out the UNION code? It is very small, but it works. I
> > think it could make a good sample for subselects.
>
> There is big difference between subqueries and queries in UNION -
> there are not dependences between UNION queries.
>
> Ok, opened issues:
>
> 1. Is using upper query' vars in all subquery levels in standard ?
I'm not certain. Let me know if you do not get an answer from someone else and I will
research it.
> 2. Is (a, b, c) OP (subselect) in standard ?
Yes. In fact, it _is_ the standard, and "a OP (subselect)" is a special case where
the parens are allowed to be omitted from a one element list.
> 3. What types of expressions (Var, Const, ...) are allowed on the left
> side of operator with subquery on the right ?
I think most expressions are allowed. The "constant OP (subselect)" case you were
asking about is just a simplified case since "(a, b, constant) OP (subselect)" where
a and b are column references should be allowed. Of course, our optimizer could
perhaps change this to "(a, b) OP (subselect where x = constant)", or for the first
example "EXISTS (subselect where x = constant)".
> 4. What types of operators should we support (=, >, ..., like, ~, ...) ?
> (My vote for all boolean operators).
Sounds good. But I'll vote with Bruce (and I'll bet you already agree) that it is
important to get an initial implementation for v6.3 which covers a little, some, or
all of the usual SQL subselect constructs. If we have to revisit this for v6.4 then
we will have the benefit of feedback from others in practical applications which
always uncovers new things to consider.
> And - did we get consensus on presentation subqueries stuff in Query,
> Expr and Var ?
> I would like to have something done in parser near Jan 17 to get
> subqueries working by Feb 1. I vote for support of all standard
> things (1. - 3.) in parser right now - if there will be no time
> to implement something like (a, b, c) then optimizer will callelog(WARN) (oh,
> sorry, - elog(ERROR)).
Great. I'd like to help with the remaining parser issues; at the moment "row_expr"
does the right thing with expression comparisions but just parses then ignores
subselect expressions. Let me know what structures you want passed back and I'll put
them in, or if you prefer put in the first one and I'll go through and clean up and
add the rest.
- Tom
From lockhart@alumni.caltech.edu Sat Jan 10 15:00:58 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id PAA00728
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 15:00:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id OAA28438 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 14:35:19 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id TAA06002;
*** ../src/backend/parser/keywords.c.orig Mon Jan 5 07:51:33 1998
--- ../src/backend/parser/keywords.c Sat Jan 10 19:22:07 1998
***************
*** 39,44 ****
--- 39,45 ----
{"alter", ALTER},
{"analyze", ANALYZE},
{"and", AND},
+ {"any", ANY},
{"append", APPEND},
{"archive", ARCHIVE},
{"as", AS},
***************
*** 178,183 ****
--- 179,185 ----
{"set", SET},
{"setof", SETOF},
{"show", SHOW},
+ {"some", SOME},
{"stdin", STDIN},
{"stdout", STDOUT},
{"substring", SUBSTRING},
--------------D8B38A0D1F78A10C0023F702--
From owner-pgsql-hackers@hub.org Sun Jan 11 01:31:13 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA12255
for <maillist@candle.pha.pa.us>; Sun, 11 Jan 1998 01:31:10 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA20396 for <maillist@candle.pha.pa.us>; Sun, 11 Jan 1998 01:10:48 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id BAA22176; Sun, 11 Jan 1998 01:03:15 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Sun, 11 Jan 1998 01:02:34 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id BAA22151 for pgsql-hackers-outgoing; Sun, 11 Jan 1998 01:02:26 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id BAA22077 for <hackers@postgresql.org>; Sun, 11 Jan 1998 01:01:05 -0500 (EST)
In-Reply-To: <34B7AD8C.5ED59CB5@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 11, 98 00:19:08 am
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> I would like to have something done in parser near Jan 17 to get
> subqueries working by Feb 1. I vote for support of all standard
> things (1. - 3.) in parser right now - if there will be no time
> to implement something like (a, b, c) then optimizer will call
> elog(WARN) (oh, sorry, - elog(ERROR)).
First, let me say I am glad we are still on schedule for Feb 1. I was
panicking because I thought we wouldn't make it in time.
> > > (is it allowable by standards ?) - in this case it's better
> > > to don't add tabA to 1st subselect but add tabA to second one
> > > and change tabA.col3 in 1st to reference col3 in 2nd subquery temp table -
> > > this gives us 2-tables join in 1st subquery instead of 3-tables join.
> > > (And I'm still not sure that using temp tables is best of what can be
> > > done in all cases...)
> >
> > I don't see any use for temp tables in subselects anymore. After having
> > implemented UNIONS, I now see how much can be done in the upper
> > optimizer. I see you just putting the subquery PLAN into the proper
> > place in the plan tree, with some proper JOIN nodes for IN, NOT IN.
>
> When saying about temp tables, I meant tables created by node Material
> for subquery plan. This is one of two ways - run subquery once for all
> possible upper plan tuples and then just join result table with upper
> query. Another way is re-run subquery for each upper query tuple,
> without temp table but may be with caching results by some ways.
> Actually, there is special case - when subquery can be alternatively
> formulated as joins, - but this is just special case.
This is interesting. It really only applies for correlated subqueries,
and certainly it may help sometimes to just evaluate the subquery for
valid values that are going to come from the upper query than for all
possible values. Perhaps we can use the 'cost' value of each query to
decide how to handle this.
>
> > > > In the parent query, to parse the WHERE clause, we create a new operator
> > > > type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
> > > ^^^^^^^^^^^^^^^^^^
> > > No. We have to handle (a,b,c) OP (select x, y, z ...) and
> > > '_a_constant_' OP (select ...) - I don't know is last in standards,
> > > Sybase has this.
> >
> > I have never seen this in my eight years of SQL. Perhaps we can leave
> > this for later, maybe much later.
>
> Are you saying about (a, b, c) or about 'a_constant' ?
> Again, can someone comment on are they in standards or not ?
> Tom ?
> If yes then please add parser' support for them now...
OK, Thomas says it is, so we will put in as much code as we can to handle
it.
> Should we say users that subselect will work for standard data types only ?
> I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
> Is there difference between handling = ANY and ~ ANY ? I don't see any.
> Currently we can't get IN working properly for boxes (and may be for others too)
> and I don't like to try to resolve these problems now, but hope that someday
> we'll be able to do this. At the moment - just convert IN into = ANY and
> NOT IN into <> ALL in parser.
OK.
>
> (BTW, do you know how DISTINCT is implemented ? It doesn't use = but
> use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
I did not know that either.
> There is big difference between subqueries and queries in UNION -
> there are not dependences between UNION queries.
Yes, I know UNIONS are trivial compared to subselects.
>
> Ok, opened issues:
>
> 1. Is using upper query' vars in all subquery levels in standard ?
> 2. Is (a, b, c) OP (subselect) in standard ?
> 3. What types of expressions (Var, Const, ...) are allowed on the left
> side of operator with subquery on the right ?
> 4. What types of operators should we support (=, >, ..., like, ~, ...) ?
> (My vote for all boolean operators).
>
> And - did we get consensus on presentation subqueries stuff in Query,
> Expr and Var ?
OK, here are my concrete ideas on changes and structures.
I think we all agreed that Query needs new fields:
Query *parentQuery;
List *subqueries;
Maybe query level too, but I don't think so (see later ideas on Var).
We need a new Node structure, call it Sublink:
int linkType (IN, NOTIN, ANY, EXISTS, OPERATOR...)
Oid operator /* subquery must return single row */
List *lefthand; /* parent stuff */
Node *subquery; /* represents nodes from parser */
Index Subindex; /* filled in to index Query->subqueries */
Of course, the names are just suggestions. Every time we run through
the parsenodes of a query to create a Query* structure, when we do the
WHERE clause, if we come upon one of these Sublink nodes (created in the
parser), we move the supplied Query* in Sublink->subquery to a local
List variable, and we set Subquery->subindex to equal the index of the
new query, i.e. is it the first subquery we found, 1, or the second, 2,
etc.
After we have created the parent Query structure, we run through our
local List variable of subquery parsenodes we created above, and add
Query* entries to Query->subqueries. In each subquery Query*, we set
the parentQuery pointer.
Also, when parsing the subqueries, we need to keep track of correlated
references. I recommend we add a field to the Var structure:
Index sublevel; /* range table reference:
= 0 current level of query
< 0 parent above this many levels
> 0 index into subquery list
*/
This way, a Var node with sublevel 0 is the current level, and is true
in most cases. This helps us not have to change much code. sublevel =
-1 means it references the range table in the parent query. sublevel =
-2 means the parent's parent. sublevel = 2 means it references the range
table of the second entry in Query->subqueries. Varno and varattno are
still meaningful. Of course, we can't reference variables in the
subqueries from the parent in the parser code, but Vadim may want to.
When doing a Var lookup in the parser, we look in the current level
first, but if not found, if it is a subquery, we can look at the parent
and parent's parent to set the sublevel, varno, and varatno properly.
We create no phantom range table entries in the subquery, and no phantom
target list entries. We can leave that all for the upper optimizer.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Tue Dec 9 12:14:09 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id MAA16186
for <maillist@candle.pha.pa.us>; Tue, 9 Dec 1997 12:14:05 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id MAA17524; Tue, 9 Dec 1997 12:05:31 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Tue, 09 Dec 1997 12:05:01 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id MAA17316 for pgsql-hackers-outgoing; Tue, 9 Dec 1997 12:04:55 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id MAA17304 for <hackers@postgresql.org>; Tue, 9 Dec 1997 12:04:40 -0500 (EST)
> Could we try to do the subselect/join/union features for 6.3? I know you
> have been looking at it, and found the deepest parts of the backend to
> be a bit murky. I'm not familiar with that area at all, but perhaps we
> could divert Vadim for a week or two or three when he has some time.
^^^^^
More realistic... And this is for initial release only: tuning performance
of subselects is very hard, long work.
Ok - I'm ready to do subselects for 6.3 but this means that foreign keys
may appear in 6.4 only. And I'll need in help: could someone add support
for them in parser ? Not handling - but parsing and common checking.
Also, it would be nice to have better temp tables implementation
(without affecting pg_class etc) - node material need in query-level
temp tables anyway. I'd really like to see temp table files created
only when its data must go to disk due to local buffer pool is full
and can't more keep table data in memory. Also, local buffer manager
should be re-written to use hash table (like shared bufmgr) for buffer search,
not sequential scan as now (this is item for TODO) - this will speed up
things and allow to use more than 64 local buffers.
I'm still sure that handling subselects in parser is not right way.
And the main problem is not in execution plans (we could use tricks
to resolve this) but in performance. Example:
select b from big where b in (select s from small);
If there is no duplicates in small then this is the same as
select b from big, small where b = s;
Without index on big postgres does seq scan of big and uses hashjoin with
hash on small. Using temp table makes query only 20% slower (in my test).
But with index on big postgres uses nestloop with seq scan of small and
index scan of big => select run faster and temp table stuff makes query
2.5 times slower! In the case of duplicates in small, handling in parser
will use distinct (and so - sorting). But using hashjoin plan distinct
may be avoided! Who can analize this ? Optimizer only. He can be smart
to check is there unique index on small or not. If not - what is more
costless: nestloop with sorting or slower hashjoin without sorting.
Only optimizer can find best way to execute query, parser can't.
> Especially if we trade him for help on his favorite topics for v6.4??
Ok, I'd like to see shared catalog cache implemeted in 6.4... -:)
Vadim
From owner-pgsql-hackers@hub.org Fri Dec 19 00:58:54 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA25460
for <maillist@candle.pha.pa.us>; Fri, 19 Dec 1997 00:58:52 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id AAA27667; Fri, 19 Dec 1997 00:54:39 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 19 Dec 1997 00:54:09 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id AAA27633 for pgsql-hackers-outgoing; Fri, 19 Dec 1997 00:54:04 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id AAA27623 for <hackers@postgresql.org>; Fri, 19 Dec 1997 00:53:53 -0500 (EST)
In-Reply-To: <349A0265.7329D4EE@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Dec 19, 97 12:13:09 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
>
> Thomas G. Lockhart wrote:
> >
> > Could we try to do the subselect/join/union features for 6.3? I know you
> > have been looking at it, and found the deepest parts of the backend to
> > be a bit murky. I'm not familiar with that area at all, but perhaps we
> > could divert Vadim for a week or two or three when he has some time.
> ^^^^^
> More realistic... And this is for initial release only: tuning performance
> of subselects is very hard, long work.
>
> Ok - I'm ready to do subselects for 6.3 but this means that foreign keys
Great.
> may appear in 6.4 only. And I'll need in help: could someone add support
> for them in parser ? Not handling - but parsing and common checking.
> Also, it would be nice to have better temp tables implementation
> (without affecting pg_class etc) - node material need in query-level
> temp tables anyway. I'd really like to see temp table files created
> only when its data must go to disk due to local buffer pool is full
> and can't more keep table data in memory. Also, local buffer manager
> should be re-written to use hash table (like shared bufmgr) for buffer search,
> not sequential scan as now (this is item for TODO) - this will speed up
> things and allow to use more than 64 local buffers.
>
> I'm still sure that handling subselects in parser is not right way.
> And the main problem is not in execution plans (we could use tricks
> to resolve this) but in performance. Example:
>
> select b from big where b in (select s from small);
>
> If there is no duplicates in small then this is the same as
>
> select b from big, small where b = s;
>
> Without index on big postgres does seq scan of big and uses hashjoin with
> hash on small. Using temp table makes query only 20% slower (in my test).
> But with index on big postgres uses nestloop with seq scan of small and
> index scan of big => select run faster and temp table stuff makes query
> 2.5 times slower! In the case of duplicates in small, handling in parser
> will use distinct (and so - sorting). But using hashjoin plan distinct
> may be avoided! Who can analize this ? Optimizer only. He can be smart
> to check is there unique index on small or not. If not - what is more
> costless: nestloop with sorting or slower hashjoin without sorting.
> Only optimizer can find best way to execute query, parser can't.
>
OK, let me comment on this. Let's take your example:
> select b from big where b in (select s from small);
>
> If there is no duplicates in small then this is the same as
>
> select b from big, small where b = s;
My idea was to do this:
select distinct s into temp table small2 from small;
select b from big,small2 where b = s;
And let the optimizer decide how to do the join. Is this what you are
saying?
The problem I see is that the temp table is already distinct, and was
sorted to do that, but you can't pass that information into the
optimizer. Is that the problem with using the parser?
But you want the temp table never to hit disk unless it has to, but that
will not work unless we do a really good job with temp tables.
Also NOT IN will need some type of non-join operator, perhaps a flag in
the Plan to say "look for a match, but only output if you find it." How
do we do that?
We definately need temp tables, and I think we can stuff it into the
cache as LOCAL, which will make it usable without adding to pg_class.
Perhaps if we create a special Plan in the optimizer called IN, and we
have the outer and inner queries as plans, and work that plan into the
executor.
The problem with that is we need to specify a way to join the two plans,
and the same logic that determines what type of join to do can this too.
Maybe that's why you wanted stuff done in the optimizer and not the
parser.
At least now, I understand enough to come up with ideas, and can
understand what you are saying.
> > Especially if we trade him for help on his favorite topics for v6.4??
>
> Ok, I'd like to see shared catalog cache implemeted in 6.4... -:)
>
> Vadim
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Fri Dec 19 01:00:58 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA25512
for <maillist@candle.pha.pa.us>; Fri, 19 Dec 1997 01:00:56 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id AAA28102; Fri, 19 Dec 1997 00:56:52 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 19 Dec 1997 00:56:40 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id AAA28077 for pgsql-hackers-outgoing; Fri, 19 Dec 1997 00:56:36 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id AAA28065 for <hackers@postgresql.org>; Fri, 19 Dec 1997 00:56:19 -0500 (EST)
> > Ok - I'm ready to do subselects for 6.3 but this means that foreign keys
> > may appear in 6.4 only. And I'll need in help: could someone add support
> > for them in parser ? Not handling - but parsing and common checking.
>
> Yes, I've already added subselect syntax in the parser, but we will need to
> modify or add to the parse tree nodes to push that past the parser into the
> backend. I'm happy to focus on that, since I understand those pieces pretty well.
Nice!
> There are several places where "subselect syntax" is used: subselects and unions
> come to mind right away. If you have an opinion on how the parse nodes should be
> structured I can start with that, or I can just put something in and then modify
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It's ok for me.
> it as you need later. Do you see unions as being similar to subselects, or are
> they a separate problem? To me, they seem like a simpler case since (perhaps) not
> as much optimization and internal reorganizing needs to happen.
I didn't think about unions at all... Yes, it's simpler to implement.
BTW, I recall Bruce mentioned that unions are used for selects from
superclass and all descendant classes (select ... from table* ) - maybe
something is already implemented ? Bruce ?
>
> > Also, it would be nice to have better temp tables implementation
> > (without affecting pg_class etc) - node material need in query-level
> > temp tables anyway. I'd really like to see temp table files created
> > only when its data must go to disk due to local buffer pool is full
> > and can't more keep table data in memory.
>
> This sounds very desirable. I noticed that there are, or used to be, multiple
> storage managers. Could a manager for temporary storage be written which stores
> things in memory until it gets too big and then go to disk? Could that manager
> use the mm and md managers internally? Or is all of that at too low a level to be
> helpful for this problem?
mm uses shmem... This feature could be implemented in local bufmgr
directly: when requested buffer is not found in pool and there is no free,
!dirty buffer then try to find some dirty buffer of created relation, flush
it to disk and use (exception below); if no such buffer -> create some relation
(and flush 1st block); exception: also create some relation if # of buffers
occupied by already created relations is too small (just to do not break
buffering of created relations).
(Note, that using some additional in-memory storage manager will cause
keeping some buffers in-memory twice - in local pool and in manager.
The way above is using local bufmgr as storage manager).
> >
> > I'm still sure that handling subselects in parser is not right way.
> > And the main problem is not in execution plans (we could use tricks
> > to resolve this) but in performance.
>
> Seems to me that the subselect needs to stay untransformed (i.e. executable but
> non-optimized) so that an optimizer can independently decide how to transform for
> faster execution. That way, in the first implementation we have reliable but
> stupid execution, but then can add a subselect optimizer which looks for cases
> which can be transformed to run faster.
Yes, I believe that this is right way.
>
> > > Especially if we trade him for help on his favorite topics for v6.4??
> >
> > Ok, I'd like to see shared catalog cache implemeted in 6.4... -:)
>
> Sure. (Tell me what it is later :)
Ok -:)
Vadim
From vadim@sable.krasnoyarsk.su Tue Dec 23 04:01:21 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA08884
for <maillist@candle.pha.pa.us>; Tue, 23 Dec 1997 04:01:18 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id DAA24250 for <maillist@candle.pha.pa.us>; Tue, 23 Dec 1997 03:57:12 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA23028;
> > I didn't think about unions at all... Yes, it's simpler to implement.
> > BTW, I recall Bruce mentioned that unions are used for selects from
> > superclass and all descendant classes (select ... from table* ) - maybe
> > something is already implemented ? Bruce ?
>
> Yes, it is already there. See optimizer/prep/prepunion.c, and see the
> call to it from optimizer/plan/planner.c. The current source tree has a
> cleaned up version that will be easier to understand. Basically, if
> there are any inherited tables, it calls prepunion, and and cycles
> through each inherited table, copying the Query plan, and calling the
> planner() for each one, then it returns to the planner() to so sorting
> and uniqueness. I am working on fixing aggregates.
Could you try with unions ?
I would like to concentrate on single thing - subqueries.
>
> > mm uses shmem... This feature could be implemented in local bufmgr
> > directly: when requested buffer is not found in pool and there is no free,
> > !dirty buffer then try to find some dirty buffer of created relation, flush
> > it to disk and use (exception below); if no such buffer -> create some relation
> > (and flush 1st block); exception: also create some relation if # of buffers
> > occupied by already created relations is too small (just to do not break
> > buffering of created relations).
> > (Note, that using some additional in-memory storage manager will cause
> > keeping some buffers in-memory twice - in local pool and in manager.
> > The way above is using local bufmgr as storage manager).
>
> In the psort code, we do a nice job of keeping the stuff in files or
> memory. Seems to work well. Can we use that somehow? Perhaps make it
> a separate module, or just force a psort rather than a hash!
I would like to be not restricted to psort only, but use what is better
in each case. I even can foresee using indices on temp tables: we could
put data in index without putting data in table itself!
In any case, we can leave in-memory tables for future.
Vadim
From owner-pgsql-hackers@hub.org Tue Dec 23 04:31:23 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA09186
for <maillist@candle.pha.pa.us>; Tue, 23 Dec 1997 04:31:20 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id EAA24391 for <maillist@candle.pha.pa.us>; Tue, 23 Dec 1997 04:04:44 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id EAA06421; Tue, 23 Dec 1997 04:00:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Tue, 23 Dec 1997 03:58:36 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id DAA06163 for pgsql-hackers-outgoing; Tue, 23 Dec 1997 03:58:32 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.5/8.7.5) with ESMTP id DAA06151 for <hackers@postgresql.org>; Tue, 23 Dec 1997 03:58:02 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA23028;
> > I didn't think about unions at all... Yes, it's simpler to implement.
> > BTW, I recall Bruce mentioned that unions are used for selects from
> > superclass and all descendant classes (select ... from table* ) - maybe
> > something is already implemented ? Bruce ?
>
> Yes, it is already there. See optimizer/prep/prepunion.c, and see the
> call to it from optimizer/plan/planner.c. The current source tree has a
> cleaned up version that will be easier to understand. Basically, if
> there are any inherited tables, it calls prepunion, and and cycles
> through each inherited table, copying the Query plan, and calling the
> planner() for each one, then it returns to the planner() to so sorting
> and uniqueness. I am working on fixing aggregates.
Could you try with unions ?
I would like to concentrate on single thing - subqueries.
>
> > mm uses shmem... This feature could be implemented in local bufmgr
> > directly: when requested buffer is not found in pool and there is no free,
> > !dirty buffer then try to find some dirty buffer of created relation, flush
> > it to disk and use (exception below); if no such buffer -> create some relation
> > (and flush 1st block); exception: also create some relation if # of buffers
> > occupied by already created relations is too small (just to do not break
> > buffering of created relations).
> > (Note, that using some additional in-memory storage manager will cause
> > keeping some buffers in-memory twice - in local pool and in manager.
> > The way above is using local bufmgr as storage manager).
>
> In the psort code, we do a nice job of keeping the stuff in files or
> memory. Seems to work well. Can we use that somehow? Perhaps make it
> a separate module, or just force a psort rather than a hash!
I would like to be not restricted to psort only, but use what is better
in each case. I even can foresee using indices on temp tables: we could
put data in index without putting data in table itself!
In any case, we can leave in-memory tables for future.
Vadim
From aixssd!darrenk@abs.net Thu Dec 5 10:30:53 1996
Received: from abs.net (root@u1.abs.net [207.114.0.130]) by candle.pha.pa.us (8.8.3/8.7.3) with ESMTP id KAA06591 for <maillist@candle.pha.pa.us>; Thu, 5 Dec 1996 10:30:43 -0500 (EST)
Received: from aixssd.UUCP (nobody@localhost) by abs.net (8.8.3/8.7.3) with UUCP id KAA01387 for maillist@candle.pha.pa.us; Thu, 5 Dec 1996 10:13:56 -0500 (EST)
Received: by aixssd (AIX 3.2/UCB 5.64/4.03)
id AA36963; Thu, 5 Dec 1996 10:10:24 -0500
Received: by ceodev (AIX 4.1/UCB 5.64/4.03)
id AA34942; Thu, 5 Dec 1996 10:07:56 -0500
Date: Thu, 5 Dec 1996 10:07:56 -0500
From: aixssd!darrenk@abs.net (Darren King)
Message-Id: <9612051507.AA34942@ceodev>
To: maillist@candle.pha.pa.us
Subject: Subselect info.
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Md5: jaWdPH2KYtdr7ESzqcOp5g==
Status: OR
> Any of them deal with implementing subselects?
There's a white paper at the www.sybase.com that might
help a little. It's just a copy of a presentation
given by the optimizer guru there. Nothing code-wise,
but he gives a few ways of flattening them with temp
tables, etc...
Darren
From vadim@sable.krasnoyarsk.su Thu Aug 21 23:42:50 1997
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id XAA04109
for <maillist@candle.pha.pa.us>; Thu, 21 Aug 1997 23:42:43 -0400 (EDT)
Received: from www.krasnet.ru (localhost [127.0.0.1]) by www.krasnet.ru (8.7.5/8.7.3) with SMTP id MAA04399; Fri, 22 Aug 1997 12:04:31 +0800 (KRD)
> this will allow to use 'outer' & 'inner' things for subselects
> latter, without confusion. My hope is that we may change Executor
Or may be use 'high' & 'low' for subselecs (to avoid confusion
with outter hoins).
> very easy by adding outer/inner plans/TupleSlots to
> EState, CommonState, JoinState, etc and by doing node
> processing in right order.
^^^^^^^^^^^^^^
Rule is easy:
1. Uncorrelated subselect - do 'low' plan node first
2. Correlated - do left/right first
- just some flag in structures.
Vadim
From owner-pgsql-hackers@hub.org Thu Oct 30 17:02:30 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id RAA09682
for <maillist@candle.pha.pa.us>; Thu, 30 Oct 1997 17:02:28 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id QAA20688; Thu, 30 Oct 1997 16:58:40 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 30 Oct 1997 16:58:24 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id QAA20615 for pgsql-hackers-outgoing; Thu, 30 Oct 1997 16:58:17 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id QAA20495 for <hackers@postgreSQL.org>; Thu, 30 Oct 1997 16:57:54 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id QAA07726
for hackers@postgreSQL.org; Thu, 30 Oct 1997 16:50:29 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Thu, 30 Oct 1997 16:50:29 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
The only thing I have to add to what I had written earlier is that I
think it is best to have these subqueries executed as early in query
execution as possible.
Every piece of the backend: parser, optimizer, executor, is designed to
work on a single query. The earlier we can split up the queries, the
better those pieces will work at doing their job. You want to be able
to use the parser and optimizer on each part of the query separately, if
you can.
Forwarded message:
> I have done some thinking about subselects. There are basically two
> issues:
>
> Does the query return one row or several rows? This can be
> determined by seeing if the user uses equals on 'IN' to join the
> subquery.
>
> Is the query correlated, meaning "Does the subquery reference
> values from the outer query?"
>
> (We already have the third type of subquery, the INSERT...SELECT query.)
>
> So we have these four combinations:
>
> 1) one row, no correlation
> 2) multiple rows, no correlation
> 3) one row, correlated
> 4) multiple rows, correlated
>
>
> With #1, we can execute the subquery, get the value, replace the
> subquery with the constant returned from the subquery, and execute the
> outer query.
>
> With #2, we can execute the subquery and put the result into a temporary
> table. We then rewrite the outer query to access the temporary table
> and replace the subquery with the column name from the temporary table.
> We probabally put an index on the temp. table, which has only one
> column, because a subquery can only return one column. We remove the
> temp. table after query execution.
>
> With #3 and #4, we potentially need to execute the subquery for every
> row returned by the outer query. Performance would be horrible for
> anything but the smallest query. Another way to handle this is to
> execute the subquery WITHOUT using any of the outer-query columns to
> restrict the WHERE clause, and add those columns used to join the outer
> variables into the target list of the subquery. So for query:
>
> select t1.name
> from tab t1
> where t1.age = (select max(t2.age)
> from tab2
> where tab2.name = t1.name)
>
> Execute the subquery and put it in a temporary table:
>
> select t2.name, max(t2.age)
> into table temp999
> from tab2
> where tab2.name = t1.name
>
> create index i_temp999 on temp999 (name)
>
> Then re-write the outer query:
>
> select t1.name
> from tab t1, temp999
> where t1.age = temp999.age and
> t1.name = temp999.name
>
> The only problem here is that the subselect is running for all entries
> in tab2, even if the outer query is only going to need a few rows.
> Determining whether to execute the subquery each time, or create a temp.
> table is often difficult to determine. Even some non-correlated
> subqueries are better to execute for each row rather the pre-execute the
> entire subquery, expecially if the outer query returns few rows.
>
> One requirement to handle these issues is better column statistics,
> which I am working on.
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Fri Oct 31 22:30:58 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id WAA15643
for <maillist@candle.pha.pa.us>; Fri, 31 Oct 1997 22:30:56 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id WAA24379 for <maillist@candle.pha.pa.us>; Fri, 31 Oct 1997 22:06:08 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id WAA15503; Fri, 31 Oct 1997 22:03:40 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 31 Oct 1997 22:01:38 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id WAA14136 for pgsql-hackers-outgoing; Fri, 31 Oct 1997 22:01:29 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id WAA13866 for <hackers@postgreSQL.org>; Fri, 31 Oct 1997 22:00:53 -0500 (EST)
In-Reply-To: <199710302150.QAA07726@candle.pha.pa.us> from "Bruce Momjian" at Oct 30, 97 04:50:29 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
One more issue I thought of. You can have multiple subselects in a
single query, and subselects can have their own subselects.
This makes it particularly important that we define a system that always
is able to process the subselect BEFORE the upper select. This will
allow use to handle all these cases without limitations.
>
> The only thing I have to add to what I had written earlier is that I
> think it is best to have these subqueries executed as early in query
> execution as possible.
>
> Every piece of the backend: parser, optimizer, executor, is designed to
> work on a single query. The earlier we can split up the queries, the
> better those pieces will work at doing their job. You want to be able
> to use the parser and optimizer on each part of the query separately, if
> you can.
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From hannu@trust.ee Sun Nov 2 10:33:33 1997
Received: from sid.trust.ee (sid.trust.ee [194.204.23.180])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA27619
for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 10:32:04 -0500 (EST)
Received: from sid.trust.ee (wink.trust.ee [194.204.23.184])
by sid.trust.ee (8.8.5/8.8.5) with ESMTP id RAA02233;
Sun, 2 Nov 1997 17:30:11 +0200
Message-ID: <345C9BFD.986C68AA@sid.trust.ee>
Date: Sun, 02 Nov 1997 17:27:57 +0200
From: Hannu Krosing <hannu@trust.ee>
X-Mailer: Mozilla 4.02 [en] (Win95; I)
MIME-Version: 1.0
To: hackers-digest@postgresql.org
CC: maillist@candle.pha.pa.us
Subject: Re: [HACKERS] subselects
References: <199711010401.XAA09216@hub.org>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Status: OR
> Date: Fri, 31 Oct 1997 21:37:06 +1900 (EST)
> From: Bruce Momjian <maillist@candle.pha.pa.us>
> Subject: Re: [HACKERS] subselects
>
> One more issue I thought of. You can have multiple subselects in a
> single query, and subselects can have their own subselects.
>
> This makes it particularly important that we define a system that always
> is able to process the subselect BEFORE the upper select. This will
> allow use to handle all these cases without limitations.
This would severely limit what subselects can be used for as you can't useany of the fields in the upper select in a
search criteria for the subselect,
for example you can't do
update parts p1
set parts.current_id = (
select new_id
from parts p2
where p1.old_id = p2.new_id);or
select id, price, (select sum(price) from parts p2 where p1.id=p2.id) as totalprice
from parts p1;
there may be of course ways to rewrite these queries (which the optimiser should do
if it can) but IMHO, these kinds of subselects should still be allowed
> > The only thing I have to add to what I had written earlier is that I
> > think it is best to have these subqueries executed as early in query
> > execution as possible.
> >
> > Every piece of the backend: parser, optimizer, executor, is designed to
> > work on a single query. The earlier we can split up the queries, the
> > better those pieces will work at doing their job. You want to be able
> > to use the parser and optimizer on each part of the query separately, if
> > you can.
> >
>
Hannu
From vadim@sable.krasnoyarsk.su Sun Nov 2 21:30:59 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id VAA14831
for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 21:30:57 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id VAA19683 for <maillist@candle.pha.pa.us>; Sun, 2 Nov 1997 21:20:13 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id JAA17259; Mon, 3 Nov 1997 09:22:38 +0700 (KRS)
> > > One more issue I thought of. You can have multiple subselects in a
> > > single query, and subselects can have their own subselects.
> > >
> > > This makes it particularly important that we define a system that always
> > > is able to process the subselect BEFORE the upper select. This will
> > > allow use to handle all these cases without limitations.
> >
> > This would severely limit what subselects can be used for as you can't useany of the fields in the upper select in a
> > search criteria for the subselect,
> > for example you can't do
> >
> > update parts p1
> > set parts.current_id = (
> > select new_id
> > from parts p2
> > where p1.old_id = p2.new_id);or
> >
> > select id, price, (select sum(price) from parts p2 where p1.id=p2.id) as totalprice
> > from parts p1;
> >
> > there may be of course ways to rewrite these queries (which the optimiser should do
> > if it can) but IMHO, these kinds of subselects should still be allowed
>
> I hadn't even gotten to this point yet, but it is a good thing to keep
> in mind.
>
> In these cases, as in correlated subqueries in the where clause, we will
> create a temporary table, and add the proper join fields and tables to
> the clauses. Our version of UPDATE accepts a FROM section, and we will
> certainly use this for this purpose.
We can't replace subselect with join if there is aggregate
in subselect.
Actually, I don't see any problems if we going to process subselect
like sql-funcs: non-correlated subselects can be emulated by
funcs without args, for correlated subselects parser (analyze.c)
has to change all upper query references to $1, $2,...
Vadim
From vadim@sable.krasnoyarsk.su Mon Nov 3 06:07:12 1997
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id GAA27433
for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 06:07:03 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id SAA18519; Mon, 3 Nov 1997 18:09:44 +0700 (KRS)
first tries to sort sizeof(table_a) * sizeof(table_b) tuples...
For tables big and small with 100 000 and 1000 tuples
select max(x*y), x from big, small group by x
"ate" all free 140M in my file system after 20 minutes (just for
sorting - nothing more) and was killed...
select x from big where x = cor(x);
(cor(int4) is 'select max($1*y) from small') takes 20 minutes -
this is bad too.
> >
> > Actually, I don't see any problems if we going to process subselect
> > like sql-funcs: non-correlated subselects can be emulated by
> > funcs without args, for correlated subselects parser (analyze.c)
> > has to change all upper query references to $1, $2,...
>
> Yes, logically, they are SQL functions, but aren't we going to see
> terrible performance in such circumstances. My experience is that when
^^^^^^^^^^^^^^^^^^^^
You're right.
> people are given subselects, they start to do huge jobs with them.
>
> In fact, the final solution may be to have both methods available, and
> switch between them depending on the size of the query sets. Each
> method has its advantages. The function example lets the outside query
> be executed, and only calls the subquery when needed.
>
> For large tables where the subselect is small and is the entire WHERE
> restriction, the SQL function gets call much too often. A simple join
> of the subquery result and the large table would be much better. This
> method also allows for sort/merge join of the subquery results, and
> index use.
...keep thinking...
Vadim
From owner-pgsql-hackers@hub.org Mon Nov 3 11:01:01 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id LAA03633
for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 11:00:59 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id KAA12174 for <maillist@candle.pha.pa.us>; Mon, 3 Nov 1997 10:49:42 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id KAA26203; Mon, 3 Nov 1997 10:33:32 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 03 Nov 1997 10:31:43 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id KAA25514 for pgsql-hackers-outgoing; Mon, 3 Nov 1997 10:31:36 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id KAA25449 for <hackers@postgreSQL.org>; Mon, 3 Nov 1997 10:31:23 -0500 (EST)
> first tries to sort sizeof(table_a) * sizeof(table_b) tuples...
> For tables big and small with 100 000 and 1000 tuples
>
> select max(x*y), x from big, small group by x
>
> "ate" all free 140M in my file system after 20 minutes (just for
> sorting - nothing more) and was killed...
>
> select x from big where x = cor(x);
> (cor(int4) is 'select max($1*y) from small') takes 20 minutes -
> this is bad too.
Again, my feeling is that in cases where the temp table would bomb, the
SQL function will be so slow that neither will be acceptable.
>
> > >
> > > Actually, I don't see any problems if we going to process subselect
> > > like sql-funcs: non-correlated subselects can be emulated by
> > > funcs without args, for correlated subselects parser (analyze.c)
> > > has to change all upper query references to $1, $2,...
> >
> > Yes, logically, they are SQL functions, but aren't we going to see
> > terrible performance in such circumstances. My experience is that when
> ^^^^^^^^^^^^^^^^^^^^
> You're right.
>
> > people are given subselects, they start to do huge jobs with them.
> >
> > In fact, the final solution may be to have both methods available, and
> > switch between them depending on the size of the query sets. Each
> > method has its advantages. The function example lets the outside query
> > be executed, and only calls the subquery when needed.
> >
> > For large tables where the subselect is small and is the entire WHERE
> > restriction, the SQL function gets call much too often. A simple join
> > of the subquery result and the large table would be much better. This
> > method also allows for sort/merge join of the subquery results, and
> > index use.
>
> ...keep thinking...
>
> Vadim
>
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Thu Nov 20 00:09:18 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA05239
for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 00:09:11 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id XAA13776; Wed, 19 Nov 1997 23:59:53 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Wed, 19 Nov 1997 23:58:49 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id XAA13599 for pgsql-hackers-outgoing; Wed, 19 Nov 1997 23:58:43 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id XAA13512 for <hackers@postgreSQL.org>; Wed, 19 Nov 1997 23:58:16 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id XAA03103
for hackers@postgreSQL.org; Wed, 19 Nov 1997 23:57:44 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Wed, 19 Nov 1997 23:57:44 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
I am going to overhaul all the /parser files, and I may give subselects
a try while I am in there. This is where it going to have to be done.
Two things I think I need are:
temp tables that go away at the end of a statement, so if the
query elog's out, the temp file gets destroyed
how do I implement "not in":
select * from a where x not in (select y from b)
Using <> is not going to work because that returns multiple copies of a,
one for every one that doesn't equal. It is like we need not equals,
but don't return multiple rows.
Any ideas?
--
Bruce Momjian
maillist@candle.pha.pa.us
From lockhart@alumni.caltech.edu Thu Nov 20 10:00:59 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA22019
for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 10:00:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id JAA21662 for <maillist@candle.pha.pa.us>; Thu, 20 Nov 1997 09:52:55 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id GAA22754;
> a try while I am in there. This is where it going to have to be done.
A first cut at the subselect syntax is already in gram.y. I'm sure that the
e-mail you had sent which collected several items regarding subselects
covers some of this topic. I've been thinking about subselects also, and
had thought that there must be some existing mechanisms in the backend
which can be used to help implement subselects. It seems to me that UNION
might be a good thing to implement first, because it has a fairly
well-defined set of behaviors:
select a union select b;
chooses elements from a and from b and then sorts/uniques the result.
select a union all select b;
chooses elements from a, sorts/uniques, and then adds all elements from b.
select a union select b union all select c;
evaluates left to right, and first evaluates a union b, sorts/uniques, and
then evaluates
(result) union all select c;
There are several types of subselects. Examples of some are:
1) select a.f from a union select b.f from b order by 1;
Needs temporary table(s), optional sort/unique, final order by.
2) select a.f from a where a.f in (select b.f from b);
Needs temporary table(s). "in" can be first implemented by count(*) > 0 but
would be better performance to have the backend return after the first
match.
3) select a.f from a where exists (select b.f from b where b.f = a);
Need to do the select and do a subselect on _each_ of the returned values?
Again could use count(*) to help implement.
This brings up the point that perhaps the backend needs a row-counting
atomic operation and count(*) could be re-implemented using that. At the
moment count(*) is transformed to a select of OID columns and does not
quite work on table joins.
I would think that outer joins could use some of these support routines
also.
- Tom
> Two things I think I need are:
>
> temp tables that go away at the end of a statement, so if the
> query elog's out, the temp file gets destroyed
>
> how do I implement "not in":
>
> select * from a where x not in (select y from b)
>
> Using <> is not going to work because that returns multiple copies of a,
> one for every one that doesn't equal. It is like we need not equals,
> but don't return multiple rows.
>
> Any ideas?
>
> --
> Bruce Momjian
> maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Mon Dec 22 00:49:03 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA13311
for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 00:49:01 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id AAA11930; Mon, 22 Dec 1997 00:45:41 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 22 Dec 1997 00:45:17 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id AAA11756 for pgsql-hackers-outgoing; Mon, 22 Dec 1997 00:45:14 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id AAA11624 for <hackers@postgreSQL.org>; Mon, 22 Dec 1997 00:44:57 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id AAA11605
for hackers@postgreSQL.org; Mon, 22 Dec 1997 00:45:23 -0500 (EST)
To: hackers@postgreSQL.org (PostgreSQL-development)
Date: Mon, 22 Dec 1997 00:45:23 -0500 (EST)
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
OK, a few questions:
Should we use sortmerge, so we can use our psort as temp tables,
or do we use hashunique?
How do we pass the query to the optimizer? How do we represent
the range table for each, and the links between them in correlated
subqueries?
I have to think about this. Comments are welcome.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Mon Dec 22 02:01:27 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id CAA20608
for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 02:01:25 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA25136 for <maillist@candle.pha.pa.us>; Mon, 22 Dec 1997 01:37:29 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA25289; Mon, 22 Dec 1997 01:31:18 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 22 Dec 1997 01:30:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA23854 for pgsql-hackers-outgoing; Mon, 22 Dec 1997 01:30:35 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id BAA22847 for <hackers@postgreSQL.org>; Mon, 22 Dec 1997 01:30:15 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id BAA17354
for hackers@postgreSQL.org; Mon, 22 Dec 1997 01:05:04 -0500 (EST)
> > Should we use sortmerge, so we can use our psort as temp tables,
> > or do we use hashunique?
> >
> > How do we pass the query to the optimizer? How do we represent
> > the range table for each, and the links between them in correlated
> > subqueries?
> >
> > I have to think about this. Comments are welcome.
>
> One more thing. I guess I am seeing subselects as a different thing
> that temp tables. I can see people wanting to put indexes on their temp
> tables, so I think they will need more system catalog support. For
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What's the difference between temp tables and temp indices ?
Both of them are handled via catalog cache...
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 3 04:01:00 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA28565
for <maillist@candle.pha.pa.us>; Sat, 3 Jan 1998 04:00:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id DAA19242 for <maillist@candle.pha.pa.us>; Sat, 3 Jan 1998 03:47:07 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA21017;
> With UNIONs done, how are things going with you on subselects? UNIONs
> are much easier that subselects.
>
> I am stumped on how to record the subselect query information in the
> parser and stuff.
And I'm too. We definitely need in EXISTS node and may be in IN one.
Also, we have to support ANY and ALL modifiers of comparison operators
(it would be nice to support ANY and ALL for all operators returning
bool: >, =, ..., like, ~ and so on). Note, that IN is the same as
= ANY (NOT IN ==> <> ALL) assuming that '=' means EQUAL for all data types,
and so, we could avoid IN node, but I'm not sure that I like such
assumption: postgres is OO-like system allowing operators to be overriden
and so, '=' can, in theory, mean not EQUAL but something else (someday
we could allow to specify "meaning" of operator in CREATE OPERATOR) -
in short, I would like IN node.
Also, I would suggest nodes for ANY and ALL.
(I need in few days to think more about recording of this stuff...)
>
> Please let me know what I can do to help, if anything.
Thanks. As I remember, Tom also wished to work here. Tom ?
Bye,
Vadim
P.S. I'll be "on-line" Jan 5.
From owner-pgsql-hackers@hub.org Mon Jan 5 07:30:51 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id HAA05466
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 07:30:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id HAA04700; Mon, 5 Jan 1998 07:22:06 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 07:21:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id HAA02846 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 07:21:35 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.5/8.7.5) with ESMTP id HAA00903 for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 07:20:57 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id TAA24278;
> I was thinking about subselects, and how to attach the two queries.
>
> What if the subquery makes a range table entry in the outer query, and
> the query is set up like the UNION queries where we put the scans in a
> row, but in the case we put them over/under each other.
>
> And we push a temp table into the catalog cache that represents the
> result of the subquery, then we could join to it in the outer query as
> though it was a real table.
>
> Also, can't we do the correlated subqueries by adding the proper
> target/output columns to the subquery, and have the outer query
> reference those columns in the subquery range table entry.
Yes, this is a way to handle subqueries by joining to temp table.
After getting plan we could change temp table access path to
node material. On the other hand, it could be useful to let optimizer
know about cost of temp table creation (have to think more about it)...
Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
is one example of this - joining by <> will give us invalid results.
Setting special NOT EQUAL flag is not enough: subquery plan must be
always inner one in this case. The same for handling ALL modifier.
Note, that we generaly can't use aggregates here: we can't add MAX to
subquery in the case of > ALL (subquery), because of > ALL should return FALSE
if subquery returns NULL(s) but aggregates don't take NULLs into account.
>
> Maybe I can write up a sample of this? Vadim, would this help? Is this
> the point we are stuck at?
Personally, I was stuck by holydays -:)
Now I can spend ~ 8 hours ~ each day for development...
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 10:45:30 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA10769
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 10:45:28 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id KAA17823; Mon, 5 Jan 1998 10:32:00 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 10:31:45 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id KAA17757 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 10:31:38 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.5/8.7.5) with ESMTP id KAA17727 for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 10:31:06 -0500 (EST)
In-Reply-To: <34B0D3AF.F31338B3@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 5, 98 07:35:59 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> Yes, this is a way to handle subqueries by joining to temp table.
> After getting plan we could change temp table access path to
> node material. On the other hand, it could be useful to let optimizer
> know about cost of temp table creation (have to think more about it)...
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
> Setting special NOT EQUAL flag is not enough: subquery plan must be
> always inner one in this case. The same for handling ALL modifier.
> Note, that we generaly can't use aggregates here: we can't add MAX to
> subquery in the case of > ALL (subquery), because of > ALL should return FALSE
> if subquery returns NULL(s) but aggregates don't take NULLs into account.
OK, here are my ideas. First, I think you have to handle subselects in
the outer node because a subquery could have its own subquery. Also, we
now have a field in Aggreg to all us to 'usenulls'.
OK, here it is. I recommend we pass the outer and subquery through
the parser and optimizer separately.
We parse the subquery first. If the subquery is not correlated, it
should parse fine. If it is correlated, any columns we find in the
subquery that are not already in the FROM list, we add the table to the
subquery FROM list, and add the referenced column to the target list of
the subquery.
When we are finished parsing the subquery, we create a catalog cache
entry for it called 'sub1' and make its fields match the target
list of the subquery.
In the outer query, we add 'sub1' to its target list, and change
the subquery reference to point to the new range table. We also add
WHERE clauses to do any correlated joins.
Here is a simple example:
select *
from taba
where col1 = (select col2
from tabb)
This is not correlated, and the subquery parser easily. We create a
'sub1' catalog cache entry, and add 'sub1' to the outer query FROM
clause. We also replace 'col1 = (subquery)' with 'col1 = sub1.col2'.
Here is a more complex correlated subquery:
select *
from taba
where col1 = (select col2
from tabb
where taba.col3 = tabb.col4)
Here we must add 'taba' to the subquery's FROM list, and add col3 to the
target list of the subquery. After we parse the subquery, add 'sub1' to
the FROM list of the outer query, change 'col1 = (subquery)' to 'col1 =
sub1.col2', and add to the outer WHERE clause 'AND taba.col3 = sub1.col3'.
THe optimizer will do the correlation for us.
In the optimizer, we can parse the subquery first, then the outer query,
and then replace all 'sub1' references in the outer query to use the
subquery plan.
I realize making merging the two plans and doing IN and NOT IN is the
real challenge, but I hoped this would give us a start.
What do you think?
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Mon Jan 5 15:02:46 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id PAA28690
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 15:02:44 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id OAA08811 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 14:28:43 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id CAA24904;
> > always inner one in this case. The same for handling ALL modifier.
> > Note, that we generaly can't use aggregates here: we can't add MAX to
> > subquery in the case of > ALL (subquery), because of > ALL should return FALSE
> > if subquery returns NULL(s) but aggregates don't take NULLs into account.
>
> OK, here are my ideas. First, I think you have to handle subselects in
> the outer node because a subquery could have its own subquery. Also, we
I hope that this is no matter: if results of subquery (with/without sub-subqueries)
will go into temp table then this table will be re-scanned for each outer tuple.
> now have a field in Aggreg to all us to 'usenulls'.
^^^^^^^^
This can't help:
vac=> select * from x;
y
-
1
2
3
<<< this is NULL
(4 rows)
vac=> select max(y) from x;
max
---
3
==> we can't replace
select * from A where A.a > ALL (select y from x);
^^^^^^^^^^^^^^^
(NULL will be returned and so A.a > ALL is FALSE - this is what
Sybase does, is it right ?)
with
select * from A where A.a > (select max(y) from x);
^^^^^^^^^^^^^^^^^^^^
just because of we lose knowledge about NULLs here.
Also, I would like to handle ANY and ALL modifiers for all bool
operators, either built-in or user-defined, for all data types -
isn't PostgreSQL OO-like RDBMS -:)
> OK, here it is. I recommend we pass the outer and subquery through
> the parser and optimizer separately.
I don't like this. I would like to get parse-tree from parser for
entire query and let optimizer (on upper level) decide how to rewrite
parse-tree and what plans to produce and how these plans should be
merged. Note, that I don't object your methods below, but only where
to place handling of this. I don't understand why should we add
new part to the system which will do optimizer' work (parse-tree -->
execution plan) and deal with optimizer nodes. Imho, upper optimizer
level is nice place to do this.
>
> We parse the subquery first. If the subquery is not correlated, it
> should parse fine. If it is correlated, any columns we find in the
> subquery that are not already in the FROM list, we add the table to the
> subquery FROM list, and add the referenced column to the target list of
> the subquery.
>
> When we are finished parsing the subquery, we create a catalog cache
> entry for it called 'sub1' and make its fields match the target
> list of the subquery.
>
> In the outer query, we add 'sub1' to its target list, and change
> the subquery reference to point to the new range table. We also add
> WHERE clauses to do any correlated joins.
...
> Here is a more complex correlated subquery:
>
> select *
> from taba
> where col1 = (select col2
> from tabb
> where taba.col3 = tabb.col4)
>
> Here we must add 'taba' to the subquery's FROM list, and add col3 to the
> target list of the subquery. After we parse the subquery, add 'sub1' to
> the FROM list of the outer query, change 'col1 = (subquery)' to 'col1 =
> sub1.col2', and add to the outer WHERE clause 'AND taba.col3 = sub1.col3'.
> THe optimizer will do the correlation for us.
>
> In the optimizer, we can parse the subquery first, then the outer query,
> and then replace all 'sub1' references in the outer query to use the
> subquery plan.
>
> I realize making merging the two plans and doing IN and NOT IN is the
^^^^^^^^^^^^^^^^^^^^^
This is very easy to do! As I already said we have just change sub1
access path (SeqScan of sub1) with SeqScan of Material node with
subquery plan.
> real challenge, but I hoped this would give us a start.
Decision about how to record subquery stuff in to parse-tree
would be very good start -:)
BTW, note that for _expression_ subqueries (which are introduced without
IN, EXISTS, ALL, ANY - this follows Sybase' naming) - as in your examples -
we have to check that subquery returns single tuple...
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 20:31:03 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id UAA06836
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:31:01 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id TAA29980 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 19:56:05 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28044; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:16 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27203 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:02 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27049 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:30 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09337
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:31:04 -0500 (EST)
One thought to follow this way: RULEs (and so - VIEWs) are handled by using
Query - how else can we implement VIEWs on selects with subqueries ?
BTW, is
select * from A where (select TRUE from B);
valid syntax ?
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 5 18:00:57 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id SAA03296
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:00:55 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id RAA20716 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 17:22:21 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id FAA25094;
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
>
> What is you approach towards this problem?
Actually, this is problem of ALL modifier (NOT IN is _not_equal_ ALL)
and so, we have to have not just NOT EQUAL flag but some ALL node
with modified operator.
After that, one way is put subquery into inner plan of an join node
to be sure that for an outer tuple all corresponding subquery tuples
will be tested with modified operator (this will require either
changing code of all join nodes or addition of new plan type - we'll see)
and another way is ... suggested by you:
> I got an idea that one could reverse the order,
> that is execute the outer first into a temptable
> and delete from that according to the result of the
> subquery and then return it.
> Probably this is too raw and slow. ;-)
This will be faster in some cases (when subquery returns many results
and there are "not so many" results from outer query) - thanks for idea!
>
> Personally, I was stuck by holydays -:)
> Now I can spend ~ 8 hours ~ each day for development...
>
> Oh, isn't it christmas eve right now in Russia?
Due to historic reasons New Year is mu-u-u-uch popular
holiday in Russia -:)
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 19:32:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id TAA05070
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 19:32:57 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id SAA26847 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:59:43 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28045; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:40 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27280 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:25 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27030 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:25 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09438
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:35:43 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id FAA25094;
> Unfortunately, not all subqueries can be handled by "normal" joins: NOT IN
> is one example of this - joining by <> will give us invalid results.
>
> What is you approach towards this problem?
Actually, this is problem of ALL modifier (NOT IN is _not_equal_ ALL)
and so, we have to have not just NOT EQUAL flag but some ALL node
with modified operator.
After that, one way is put subquery into inner plan of an join node
to be sure that for an outer tuple all corresponding subquery tuples
will be tested with modified operator (this will require either
changing code of all join nodes or addition of new plan type - we'll see)
and another way is ... suggested by you:
> I got an idea that one could reverse the order,
> that is execute the outer first into a temptable
> and delete from that according to the result of the
> subquery and then return it.
> Probably this is too raw and slow. ;-)
This will be faster in some cases (when subquery returns many results
and there are "not so many" results from outer query) - thanks for idea!
>
> Personally, I was stuck by holydays -:)
> Now I can spend ~ 8 hours ~ each day for development...
>
> Oh, isn't it christmas eve right now in Russia?
Due to historic reasons New Year is mu-u-u-uch popular
holiday in Russia -:)
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 5 18:00:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id SAA03300
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 18:00:57 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id RAA21652 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 17:42:15 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id GAA25129;
> > and SubSelect (Query) here (as possible case).
> >
> > One thought to follow this way: RULEs (and so - VIEWs) are handled by using
> > Query - how else can we implement VIEWs on selects with subqueries ?
>
> Views are stored as nodeout structures, and are merged into the query's
> from list, target list, and where clause. I am working out
> readfunc,outfunc now to make sure they are up-to-date with all the
> current fields.
Nice! This stuff was out-of-date for too long time.
> > BTW, is
> >
> > select * from A where (select TRUE from B);
> >
> > valid syntax ?
>
> I don't think so.
And so, *rexpr can be of Query type only for oper "in" OP, IN, NOT IN,
ANY, ALL, EXISTS - well.
(Time to sleep -:)
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 5 20:31:08 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id UAA06842
for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:31:06 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id UAA00621 for <maillist@candle.pha.pa.us>; Mon, 5 Jan 1998 20:03:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA28043; Mon, 5 Jan 1998 19:06:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 05 Jan 1998 19:03:38 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA27270 for pgsql-hackers-outgoing; Mon, 5 Jan 1998 19:03:22 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA27141 for <hackers@postgresql.org>; Mon, 5 Jan 1998 19:02:50 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id RAA09919
for <hackers@postgreSQL.org>; Mon, 5 Jan 1998 17:54:47 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id GAA25129;
> > and SubSelect (Query) here (as possible case).
> >
> > One thought to follow this way: RULEs (and so - VIEWs) are handled by using
> > Query - how else can we implement VIEWs on selects with subqueries ?
>
> Views are stored as nodeout structures, and are merged into the query's
> from list, target list, and where clause. I am working out
> readfunc,outfunc now to make sure they are up-to-date with all the
> current fields.
Nice! This stuff was out-of-date for too long time.
> > BTW, is
> >
> > select * from A where (select TRUE from B);
> >
> > valid syntax ?
>
> I don't think so.
And so, *rexpr can be of Query type only for oper "in" OP, IN, NOT IN,
ANY, ALL, EXISTS - well.
(Time to sleep -:)
Vadim
From owner-pgsql-hackers@hub.org Thu Jan 8 23:10:50 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id XAA09707
for <maillist@candle.pha.pa.us>; Thu, 8 Jan 1998 23:10:48 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id XAA19334 for <maillist@candle.pha.pa.us>; Thu, 8 Jan 1998 23:08:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id XAA14375; Thu, 8 Jan 1998 23:03:29 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 08 Jan 1998 23:03:10 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id XAA14345 for pgsql-hackers-outgoing; Thu, 8 Jan 1998 23:03:06 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id XAA14008 for <hackers@postgreSQL.org>; Thu, 8 Jan 1998 23:00:50 -0500 (EST)
Vadim, I know you are still thinking about subselects, but I have some
more clarification that may help.
We have to add phantom range table entries to correlated subselects so
they will pass the parser. We might as well add those fields to the
target list of the subquery at the same time:
select *
from taba
where col1 = (select col2
from tabb
where taba.col3 = tabb.col4)
becomes:
select *
from taba
where col1 = (select col2, tabb.col4 <---
from tabb, taba <---
where taba.col3 = tabb.col4)
We add a field to TargetEntry and RangeTblEntry to mark the fact that it
was entered as a correlation entry:
bool isCorrelated;
Second, we need to hook the subselect to the main query. I recommend we
add two fields to Query for this:
Query *parentQuery;
List *subqueries;
The parentQuery pointer is used to resolve field names in the correlated
subquery.
select *
from taba
where col1 = (select col2, tabb.col4 <---
from tabb, taba <---
where taba.col3 = tabb.col4)
In the query above, the subquery can be easily parsed, and we add the
subquery to the parsent's parentQuery list.
In the parent query, to parse the WHERE clause, we create a new operator
type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
right side is an index to a slot in the subqueries List.
We can then do the rest in the upper optimizer.
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Fri Jan 9 10:01:01 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA27305
for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 10:00:59 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id JAA21583 for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 09:52:17 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id WAA01623;
> Vadim, I know you are still thinking about subselects, but I have some
> more clarification that may help.
>
> We have to add phantom range table entries to correlated subselects so
> they will pass the parser. We might as well add those fields to the
> target list of the subquery at the same time:
>
> select *
> from taba
> where col1 = (select col2
> from tabb
> where taba.col3 = tabb.col4)
>
> becomes:
>
> select *
> from taba
> where col1 = (select col2, tabb.col4 <---
> from tabb, taba <---
> where taba.col3 = tabb.col4)
>
> We add a field to TargetEntry and RangeTblEntry to mark the fact that it
> was entered as a correlation entry:
>
> bool isCorrelated;
No, I don't like to add anything in parser. Example:
select *
from tabA
where col1 = (select col2
from tabB
where tabA.col3 = tabB.col4
and exists (select *
from tabC
where tabB.colX = tabC.colX and
tabC.colY = tabA.col2)
)
: a column of tabA is referenced in sub-subselect
(is it allowable by standards ?) - in this case it's better
to don't add tabA to 1st subselect but add tabA to second one
and change tabA.col3 in 1st to reference col3 in 2nd subquery temp table -
this gives us 2-tables join in 1st subquery instead of 3-tables join.
(And I'm still not sure that using temp tables is best of what can be
done in all cases...)
Instead of using isCorrelated in TE & RTE we can add
Index varlevel;
to Var node to reflect (sub)query from where this Var is come
(where is range table to find var's relation using varno). Upmost query
will have varlevel = 0, all its (dirrect) children - varlevel = 1 and so on.
^^^ ^^^^^^^^^^^^
(I don't see problems with distinguishing Vars of different children
on the same level...)
>
> Second, we need to hook the subselect to the main query. I recommend we
> add two fields to Query for this:
>
> Query *parentQuery;
> List *subqueries;
Agreed. And maybe Index queryLevel.
> In the parent query, to parse the WHERE clause, we create a new operator
> type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
^^^^^^^^^^^^^^^^^^
No. We have to handle (a,b,c) OP (select x, y, z ...) and
'_a_constant_' OP (select ...) - I don't know is last in standards,
Sybase has this.
Well,
typedef enum OpType
{
OP_EXPR, FUNC_EXPR, OR_EXPR, AND_EXPR, NOT_EXPR
+ OP_EXISTS, OP_ALL, OP_ANY
} OpType;
typedef struct Expr
{
NodeTag type;
Oid typeOid; /* oid of the type of this expr */
OpType opType; /* type of the op */
Node *oper; /* could be Oper or Func */
List *args; /* list of argument nodes */
} Expr;
OP_EXISTS: oper is NULL, lfirst(args) is SubSelect (index in subqueries
List, following your suggestion)
OP_ALL, OP_ANY:
oper is List of Oper nodes. We need in list because of data types of
a, b, c (above) can be different and so Oper nodes will be different too.
lfirst(args) is List of expression nodes (Const, Var, Func ?, a + b ?) -
left side of subquery' operator.
lsecond(args) is SubSelect.
Note, that there are no OP_IN, OP_NOTIN in OpType-s for Expr. We need in
IN, NOTIN in A_Expr (parser node), but both of them have to be transferred
by parser into corresponding ANY and ALL. At the moment we can do:
IN --> = ANY, NOT IN --> <> ALL
but this will be "known bug": this breaks OO-nature of Postgres, because of
operators can be overrided and '=' can mean s o m e t h i n g (not equality).
Example: box data type. For boxes, = means equality of _areas_ and =~
means that boxes are the same ==> =~ ANY should be used for IN.
> right side is an index to a slot in the subqueries List.
Vadim
From owner-pgsql-hackers@hub.org Fri Jan 9 17:44:04 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id RAA24779
for <maillist@candle.pha.pa.us>; Fri, 9 Jan 1998 17:44:01 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id RAA20728; Fri, 9 Jan 1998 17:32:34 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 09 Jan 1998 17:32:19 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id RAA20503 for pgsql-hackers-outgoing; Fri, 9 Jan 1998 17:32:15 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id RAA20008 for <hackers@postgresql.org>; Fri, 9 Jan 1998 17:31:24 -0500 (EST)
easy extensibility of Postgres, it replaces the PostQuel query language with an
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
extended subset of SQL.
^^^^^^^^^^^^^^^^^^^^^^
Should we say users that subselect will work for standard data types only ?
I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
Is there difference between handling = ANY and ~ ANY ? I don't see any.
Currently we can't get IN working properly for boxes (and may be for others too)
and I don't like to try to resolve these problems now, but hope that someday
we'll be able to do this. At the moment - just convert IN into = ANY and
NOT IN into <> ALL in parser.
(BTW, do you know how DISTINCT is implemented ? It doesn't use = but
use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
> >
> > > right side is an index to a slot in the subqueries List.
>
> I guess the question is what can we have by February 1?
>
> I have been reading some postings, and it seems to me that subselects
> are the litmus test for many evaluators when deciding if a database
> engine is full-featured.
>
> Sorry to be so straightforward, but I want to keep hashing this around
> until we get a conclusion, so coding can start.
>
> My suggestions have been, I believe, trying to get subselects working
> with the fullest functionality by adding the least amount of code, and
> keeping the logic clean.
>
> Have you checked out the UNION code? It is very small, but it works. I
> think it could make a good sample for subselects.
There is big difference between subqueries and queries in UNION -
there are not dependences between UNION queries.
Ok, opened issues:
1. Is using upper query' vars in all subquery levels in standard ?
2. Is (a, b, c) OP (subselect) in standard ?
3. What types of expressions (Var, Const, ...) are allowed on the left
side of operator with subquery on the right ?
4. What types of operators should we support (=, >, ..., like, ~, ...) ?
(My vote for all boolean operators).
And - did we get consensus on presentation subqueries stuff in Query,
Expr and Var ?
I would like to have something done in parser near Jan 17 to get
subqueries working by Feb 1. I vote for support of all standard
things (1. - 3.) in parser right now - if there will be no time
to implement something like (a, b, c) then optimizer will call
elog(WARN) (oh, sorry, - elog(ERROR)).
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 10 12:31:05 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id MAA29045
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:31:01 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id MAA23364 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:22:30 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id AAA05725;
> Should we use sortmerge, so we can use our psort as temp tables,
> or do we use hashunique?
>
> How do we pass the query to the optimizer? How do we represent
> the range table for each, and the links between them in correlated
> subqueries?
My suggestion is just use varlevel in Var and don't put upper query'
relations into subquery range table.
Vadim
From vadim@sable.krasnoyarsk.su Sat Jan 10 13:01:00 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id NAA29357
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:00:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id MAA24030 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 12:40:02 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id AAA05741;
> > Should we use sortmerge, so we can use our psort as temp tables,
> > or do we use hashunique?
> >
> > How do we pass the query to the optimizer? How do we represent
> > the range table for each, and the links between them in correlated
> > subqueries?
>
> My suggestion is just use varlevel in Var and don't put upper query'
> relations into subquery range table.
Hmm... Sorry, it seems that I did reply to very old message - forget it.
Vadim
From lockhart@alumni.caltech.edu Sat Jan 10 13:30:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id NAA29664
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:30:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id NAA25109 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 13:05:09 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id SAA03623;
> easy extensibility of Postgres, it replaces the PostQuel query language with an
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> extended subset of SQL.
> ^^^^^^^^^^^^^^^^^^^^^^
>
> Should we say users that subselect will work for standard data types only ?
> I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
> Is there difference between handling = ANY and ~ ANY ? I don't see any.
> Currently we can't get IN working properly for boxes (and may be for others too)
> and I don't like to try to resolve these problems now, but hope that someday
> we'll be able to do this. At the moment - just convert IN into = ANY and
> NOT IN into <> ALL in parser.
>
> (BTW, do you know how DISTINCT is implemented ? It doesn't use = but
> use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
?? I didn't know that. Wouldn't we want it to eventually use "=" through a sorted
list? That would give more consistant behavior...
> > I have been reading some postings, and it seems to me that subselects
> > are the litmus test for many evaluators when deciding if a database
> > engine is full-featured.
> >
> > Sorry to be so straightforward, but I want to keep hashing this around
> > until we get a conclusion, so coding can start.
> >
> > My suggestions have been, I believe, trying to get subselects working
> > with the fullest functionality by adding the least amount of code, and
> > keeping the logic clean.
> >
> > Have you checked out the UNION code? It is very small, but it works. I
> > think it could make a good sample for subselects.
>
> There is big difference between subqueries and queries in UNION -
> there are not dependences between UNION queries.
>
> Ok, opened issues:
>
> 1. Is using upper query' vars in all subquery levels in standard ?
I'm not certain. Let me know if you do not get an answer from someone else and I will
research it.
> 2. Is (a, b, c) OP (subselect) in standard ?
Yes. In fact, it _is_ the standard, and "a OP (subselect)" is a special case where
the parens are allowed to be omitted from a one element list.
> 3. What types of expressions (Var, Const, ...) are allowed on the left
> side of operator with subquery on the right ?
I think most expressions are allowed. The "constant OP (subselect)" case you were
asking about is just a simplified case since "(a, b, constant) OP (subselect)" where
a and b are column references should be allowed. Of course, our optimizer could
perhaps change this to "(a, b) OP (subselect where x = constant)", or for the first
example "EXISTS (subselect where x = constant)".
> 4. What types of operators should we support (=, >, ..., like, ~, ...) ?
> (My vote for all boolean operators).
Sounds good. But I'll vote with Bruce (and I'll bet you already agree) that it is
important to get an initial implementation for v6.3 which covers a little, some, or
all of the usual SQL subselect constructs. If we have to revisit this for v6.4 then
we will have the benefit of feedback from others in practical applications which
always uncovers new things to consider.
> And - did we get consensus on presentation subqueries stuff in Query,
> Expr and Var ?
> I would like to have something done in parser near Jan 17 to get
> subqueries working by Feb 1. I vote for support of all standard
> things (1. - 3.) in parser right now - if there will be no time
> to implement something like (a, b, c) then optimizer will callelog(WARN) (oh,
> sorry, - elog(ERROR)).
Great. I'd like to help with the remaining parser issues; at the moment "row_expr"
does the right thing with expression comparisions but just parses then ignores
subselect expressions. Let me know what structures you want passed back and I'll put
them in, or if you prefer put in the first one and I'll go through and clean up and
add the rest.
- Tom
From lockhart@alumni.caltech.edu Sat Jan 10 15:00:58 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id PAA00728
for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 15:00:56 -0500 (EST)
Received: from golem.jpl.nasa.gov (root@gnet04.jpl.nasa.gov [128.149.70.168]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id OAA28438 for <maillist@candle.pha.pa.us>; Sat, 10 Jan 1998 14:35:19 -0500 (EST)
Received: from alumni.caltech.edu (localhost [127.0.0.1])
by golem.jpl.nasa.gov (8.8.5/8.8.5) with ESMTP id TAA06002;
*** ../src/backend/parser/keywords.c.orig Mon Jan 5 07:51:33 1998
--- ../src/backend/parser/keywords.c Sat Jan 10 19:22:07 1998
***************
*** 39,44 ****
--- 39,45 ----
{"alter", ALTER},
{"analyze", ANALYZE},
{"and", AND},
+ {"any", ANY},
{"append", APPEND},
{"archive", ARCHIVE},
{"as", AS},
***************
*** 178,183 ****
--- 179,185 ----
{"set", SET},
{"setof", SETOF},
{"show", SHOW},
+ {"some", SOME},
{"stdin", STDIN},
{"stdout", STDOUT},
{"substring", SUBSTRING},
--------------D8B38A0D1F78A10C0023F702--
From owner-pgsql-hackers@hub.org Sun Jan 11 01:31:13 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA12255
for <maillist@candle.pha.pa.us>; Sun, 11 Jan 1998 01:31:10 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA20396 for <maillist@candle.pha.pa.us>; Sun, 11 Jan 1998 01:10:48 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id BAA22176; Sun, 11 Jan 1998 01:03:15 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Sun, 11 Jan 1998 01:02:34 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id BAA22151 for pgsql-hackers-outgoing; Sun, 11 Jan 1998 01:02:26 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id BAA22077 for <hackers@postgresql.org>; Sun, 11 Jan 1998 01:01:05 -0500 (EST)
In-Reply-To: <34B7AD8C.5ED59CB5@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 11, 98 00:19:08 am
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> I would like to have something done in parser near Jan 17 to get
> subqueries working by Feb 1. I vote for support of all standard
> things (1. - 3.) in parser right now - if there will be no time
> to implement something like (a, b, c) then optimizer will call
> elog(WARN) (oh, sorry, - elog(ERROR)).
First, let me say I am glad we are still on schedule for Feb 1. I was
panicking because I thought we wouldn't make it in time.
> > > (is it allowable by standards ?) - in this case it's better
> > > to don't add tabA to 1st subselect but add tabA to second one
> > > and change tabA.col3 in 1st to reference col3 in 2nd subquery temp table -
> > > this gives us 2-tables join in 1st subquery instead of 3-tables join.
> > > (And I'm still not sure that using temp tables is best of what can be
> > > done in all cases...)
> >
> > I don't see any use for temp tables in subselects anymore. After having
> > implemented UNIONS, I now see how much can be done in the upper
> > optimizer. I see you just putting the subquery PLAN into the proper
> > place in the plan tree, with some proper JOIN nodes for IN, NOT IN.
>
> When saying about temp tables, I meant tables created by node Material
> for subquery plan. This is one of two ways - run subquery once for all
> possible upper plan tuples and then just join result table with upper
> query. Another way is re-run subquery for each upper query tuple,
> without temp table but may be with caching results by some ways.
> Actually, there is special case - when subquery can be alternatively
> formulated as joins, - but this is just special case.
This is interesting. It really only applies for correlated subqueries,
and certainly it may help sometimes to just evaluate the subquery for
valid values that are going to come from the upper query than for all
possible values. Perhaps we can use the 'cost' value of each query to
decide how to handle this.
>
> > > > In the parent query, to parse the WHERE clause, we create a new operator
> > > > type, called IN or NOT_IN, or ALL, where the left side is a Var, and the
> > > ^^^^^^^^^^^^^^^^^^
> > > No. We have to handle (a,b,c) OP (select x, y, z ...) and
> > > '_a_constant_' OP (select ...) - I don't know is last in standards,
> > > Sybase has this.
> >
> > I have never seen this in my eight years of SQL. Perhaps we can leave
> > this for later, maybe much later.
>
> Are you saying about (a, b, c) or about 'a_constant' ?
> Again, can someone comment on are they in standards or not ?
> Tom ?
> If yes then please add parser' support for them now...
OK, Thomas says it is, so we will put in as much code as we can to handle
it.
> Should we say users that subselect will work for standard data types only ?
> I don't see why subquery can't be used with ~, ~*, @@, ... operators, do you ?
> Is there difference between handling = ANY and ~ ANY ? I don't see any.
> Currently we can't get IN working properly for boxes (and may be for others too)
> and I don't like to try to resolve these problems now, but hope that someday
> we'll be able to do this. At the moment - just convert IN into = ANY and
> NOT IN into <> ALL in parser.
OK.
>
> (BTW, do you know how DISTINCT is implemented ? It doesn't use = but
> use type_out funcs and uses strcmp()... DISTINCT is standard SQL thing...)
I did not know that either.
> There is big difference between subqueries and queries in UNION -
> there are not dependences between UNION queries.
Yes, I know UNIONS are trivial compared to subselects.
>
> Ok, opened issues:
>
> 1. Is using upper query' vars in all subquery levels in standard ?
> 2. Is (a, b, c) OP (subselect) in standard ?
> 3. What types of expressions (Var, Const, ...) are allowed on the left
> side of operator with subquery on the right ?
> 4. What types of operators should we support (=, >, ..., like, ~, ...) ?
> (My vote for all boolean operators).
>
> And - did we get consensus on presentation subqueries stuff in Query,
> Expr and Var ?
OK, here are my concrete ideas on changes and structures.
I think we all agreed that Query needs new fields:
Query *parentQuery;
List *subqueries;
Maybe query level too, but I don't think so (see later ideas on Var).
We need a new Node structure, call it Sublink:
int linkType (IN, NOTIN, ANY, EXISTS, OPERATOR...)
Oid operator /* subquery must return single row */
List *lefthand; /* parent stuff */
Node *subquery; /* represents nodes from parser */
Index Subindex; /* filled in to index Query->subqueries */
Of course, the names are just suggestions. Every time we run through
the parsenodes of a query to create a Query* structure, when we do the
WHERE clause, if we come upon one of these Sublink nodes (created in the
parser), we move the supplied Query* in Sublink->subquery to a local
List variable, and we set Subquery->subindex to equal the index of the
new query, i.e. is it the first subquery we found, 1, or the second, 2,
etc.
After we have created the parent Query structure, we run through our
local List variable of subquery parsenodes we created above, and add
Query* entries to Query->subqueries. In each subquery Query*, we set
the parentQuery pointer.
Also, when parsing the subqueries, we need to keep track of correlated
references. I recommend we add a field to the Var structure:
Index sublevel; /* range table reference:
= 0 current level of query
< 0 parent above this many levels
> 0 index into subquery list
*/
This way, a Var node with sublevel 0 is the current level, and is true
in most cases. This helps us not have to change much code. sublevel =
-1 means it references the range table in the parent query. sublevel =
-2 means the parent's parent. sublevel = 2 means it references the range
table of the second entry in Query->subqueries. Varno and varattno are
still meaningful. Of course, we can't reference variables in the
subqueries from the parent in the parser code, but Vadim may want to.
When doing a Var lookup in the parser, we look in the current level
first, but if not found, if it is a subquery, we can look at the parent
and parent's parent to set the sublevel, varno, and varatno properly.
We create no phantom range table entries in the subquery, and no phantom
target list entries. We can leave that all for the upper optimizer.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Fri Nov 28 16:34:03 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id QAA17454
for <maillist@candle.pha.pa.us>; Fri, 28 Nov 1997 16:33:59 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id QAA10553; Fri, 28 Nov 1997 16:20:03 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 28 Nov 1997 16:17:50 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id QAA10116 for pgsql-hackers-outgoing; Fri, 28 Nov 1997 16:17:45 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id QAA09997 for <hackers@postgreSQL.org>; Fri, 28 Nov 1997 16:17:26 -0500 (EST)
Received: (from maillist@localhost)
by candle.pha.pa.us (8.8.5/8.8.5) id QAA17309
for hackers@postgreSQL.org; Fri, 28 Nov 1997 16:18:08 -0500 (EST)
sprintf(query,"create table test(x int); select x from test;");
doquery(query);
disconnectdb();
return 0;
}
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Sat Nov 29 05:01:01 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id FAA27942
for <maillist@candle.pha.pa.us>; Sat, 29 Nov 1997 05:00:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id EAA13666 for <maillist@candle.pha.pa.us>; Sat, 29 Nov 1997 04:35:08 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id QAA17107; Sat, 29 Nov 1997 16:38:58 +0700 (KRS)
From vadim@sable.krasnoyarsk.su Sun Nov 30 02:30:56 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id CAA15439
for <maillist@candle.pha.pa.us>; Sun, 30 Nov 1997 02:30:55 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id CAA17743 for <maillist@candle.pha.pa.us>; Sun, 30 Nov 1997 02:27:40 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id OAA18937; Sun, 30 Nov 1997 14:32:14 +0700 (KRS)
> > * ExecMaterial - generate a temporary relation
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> I understand what you are saying here. The temp table has transaction
> scope, and breaking each query into multiple commands, each with its own
> transaction scope will cause the temp table to go away.
No. I just said that there will be no ability to prepare queries with
subselects for latter execution: will be no ability to get execution plan which
could be passed to executor to get results without additional parser/planner
invocations. This ability is used by SQL-functions and SPI_prepare()/SPI_execp()
(==> PLs). RULEs don't use execution plan, but use parsed query tree (stored
in pg_rewrite) -> I foresee problems with VIEWs on queries with subselects.
Ability to have execution plans seems important to me. Other DBMS-es use
this for stored procedures and views.
Vadim
From owner-pgsql-hackers@hub.org Mon Dec 1 01:30:57 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA10903
for <maillist@candle.pha.pa.us>; Mon, 1 Dec 1997 01:30:55 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA26262 for <maillist@candle.pha.pa.us>; Mon, 1 Dec 1997 01:21:28 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA05263; Mon, 1 Dec 1997 01:02:12 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 01 Dec 1997 01:00:12 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA03357 for pgsql-hackers-outgoing; Mon, 1 Dec 1997 01:00:07 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id AAA03290 for <hackers@postgreSQL.org>; Mon, 1 Dec 1997 00:59:45 -0500 (EST)
Subject: Re: [HACKERS] querytrees and multiple statements
To: vadim@sable.krasnoyarsk.su (Vadim B. Mikheev)
Date: Mon, 1 Dec 1997 00:57:07 -0500 (EST)
Cc: hackers@postgreSQL.org
In-Reply-To: <3481167E.2781E494@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Nov 30, 97 02:32:14 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
>
> No. I just said that there will be no ability to prepare queries with
> subselects for latter execution: will be no ability to get execution plan which
> could be passed to executor to get results without additional parser/planner
> invocations. This ability is used by SQL-functions and SPI_prepare()/SPI_execp()
> (==> PLs). RULEs don't use execution plan, but use parsed query tree (stored
> in pg_rewrite) -> I foresee problems with VIEWs on queries with subselects.
>
> Ability to have execution plans seems important to me. Other DBMS-es use
> this for stored procedures and views.
>
> Vadim
>
I see what you are saying about other people calling pg_plan(). pg_plan
returns the query rewritten, and a plan, and some areas use that. I
will have to make sure I honor that functionality in any changes I make
to it. I will think more about this. I may have to add an 'execute me'
flag to it. However, I am unsure how I am going to generate 'just a
plan or rewritten query structure' without actually running the query
and having the temp table created so the rest can be parsed.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Mon Dec 1 02:00:58 1997
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id CAA11221
for <maillist@candle.pha.pa.us>; Mon, 1 Dec 1997 02:00:57 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA26994 for <maillist@candle.pha.pa.us>; Mon, 1 Dec 1997 01:55:19 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA23269; Mon, 1 Dec 1997 01:47:13 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 01 Dec 1997 01:45:31 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA22653 for pgsql-hackers-outgoing; Mon, 1 Dec 1997 01:45:25 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.5/8.7.5) with ESMTP id BAA22590 for <hackers@postgreSQL.org>; Mon, 1 Dec 1997 01:45:13 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id NAA21318; Mon, 1 Dec 1997 13:49:58 +0700 (KRS)
> > No. I just said that there will be no ability to prepare queries with
> > subselects for latter execution: will be no ability to get execution plan which
> > could be passed to executor to get results without additional parser/planner
> > invocations. This ability is used by SQL-functions and SPI_prepare()/SPI_execp()
> > (==> PLs). RULEs don't use execution plan, but use parsed query tree (stored
> > in pg_rewrite) -> I foresee problems with VIEWs on queries with subselects.
> >
> > Ability to have execution plans seems important to me. Other DBMS-es use
> > this for stored procedures and views.
> >
> > Vadim
> >
>
> I see what you are saying about other people calling pg_plan(). pg_plan
> returns the query rewritten, and a plan, and some areas use that. I
> will have to make sure I honor that functionality in any changes I make
> to it. I will think more about this. I may have to add an 'execute me'
> flag to it. However, I am unsure how I am going to generate 'just a
> plan or rewritten query structure' without actually running the query
> and having the temp table created so the rest can be parsed.
That's why I suggest to try with nodeMaterial(): this could allow to handle
subqueries on optimizer level and got single execution plan for
single user query.
Vadim
From owner-pgsql-hackers@hub.org Mon Dec 1 02:46:23 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id CAA11762
for <maillist@candle.pha.pa.us>; Mon, 1 Dec 1997 02:46:21 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id CAA11681; Mon, 1 Dec 1997 02:35:00 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 01 Dec 1997 02:33:17 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id CAA11451 for pgsql-hackers-outgoing; Mon, 1 Dec 1997 02:33:09 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id CAA11110 for <hackers@postgreSQL.org>; Mon, 1 Dec 1997 02:32:10 -0500 (EST)
Subject: Re: [HACKERS] querytrees and multiple statements
To: vadim@sable.krasnoyarsk.su (Vadim B. Mikheev)
Date: Mon, 1 Dec 1997 02:32:45 -0500 (EST)
Cc: hackers@postgreSQL.org
In-Reply-To: <34825E16.446B9B3D@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Dec 1, 97 01:49:58 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
>
> Bruce Momjian wrote:
> >
> > >
> > > No. I just said that there will be no ability to prepare queries with
> > > subselects for latter execution: will be no ability to get execution plan which
> > > could be passed to executor to get results without additional parser/planner
> > > invocations. This ability is used by SQL-functions and SPI_prepare()/SPI_execp()
> > > (==> PLs). RULEs don't use execution plan, but use parsed query tree (stored
> > > in pg_rewrite) -> I foresee problems with VIEWs on queries with subselects.
> > >
> > > Ability to have execution plans seems important to me. Other DBMS-es use
> > > this for stored procedures and views.
> > >
> > > Vadim
> > >
> >
> > I see what you are saying about other people calling pg_plan(). pg_plan
> > returns the query rewritten, and a plan, and some areas use that. I
> > will have to make sure I honor that functionality in any changes I make
> > to it. I will think more about this. I may have to add an 'execute me'
> > flag to it. However, I am unsure how I am going to generate 'just a
> > plan or rewritten query structure' without actually running the query
> > and having the temp table created so the rest can be parsed.
>
> That's why I suggest to try with nodeMaterial(): this could allow to handle
> subqueries on optimizer level and got single execution plan for
> single user query.
Can you give me more details on this? I realize I can create an empty
tmp table to get through the parser analysis stuff, but how do I do
something in nodeMaterial?
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Tue Dec 2 00:04:05 1997
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id AAA00350
for <maillist@candle.pha.pa.us>; Tue, 2 Dec 1997 00:03:58 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id MAA22889; Tue, 2 Dec 1997 12:09:57 +0700 (KRS)
> > That's why I suggest to try with nodeMaterial(): this could allow to handle
> > subqueries on optimizer level and got single execution plan for
> > single user query.
>
> Can you give me more details on this? I realize I can create an empty
> tmp table to get through the parser analysis stuff, but how do I do
> something in nodeMaterial?
* ExecMaterial
*
* The first time this is called, ExecMaterial retrieves tuples
* this node's outer subplan and inserts them into a temporary
^^^^^^^
* relation. After this is done, a flag is set indicating that
* the subplan has been materialized. Once the relation is
* materialized, the first tuple is then returned. Successive
* calls to ExecMaterial return successive tuples from the temp
* relation.
As you see, this node materializes some plan results into temp relation:
instead of doing SELECT ... INTO temp FROM ... WHERE ... you could
create Material node using plan for 'SELECT ... FROM ... WHERE ...' as
its subplan. SeqScan of this materialized relation can be used in any
join plans just like scan od normal relation, e.g. - NESTLOOP plan:
NESTLOOP
SeqScan A
SeqScan B
becomes
NESTLOOP
SeqScan
Material
...subplan here...
SeqScan B (or other Material)
and so on...
Vadim
From owner-pgsql-hackers@hub.org Tue Dec 2 01:28:02 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA02313
for <maillist@candle.pha.pa.us>; Tue, 2 Dec 1997 01:28:00 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA00346; Tue, 2 Dec 1997 01:03:55 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Tue, 02 Dec 1997 01:03:04 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA28750 for pgsql-hackers-outgoing; Tue, 2 Dec 1997 01:02:57 -0500 (EST)
Received: from candle.pha.pa.us (maillist@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id BAA28254 for <hackers@postgreSQL.org>; Tue, 2 Dec 1997 01:02:38 -0500 (EST)
Subject: Re: [HACKERS] querytrees and multiple statements
To: vadim@sable.krasnoyarsk.su (Vadim B. Mikheev)
Date: Tue, 2 Dec 1997 01:02:15 -0500 (EST)
Cc: vadim@post.krasnet.ru, hackers@postgreSQL.org
In-Reply-To: <34839824.3F54BC7E@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Dec 2, 97 12:09:56 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
>
> Bruce Momjian wrote:
> >
> > >
> > > That's why I suggest to try with nodeMaterial(): this could allow to handle
> > > subqueries on optimizer level and got single execution plan for
> > > single user query.
> >
> > Can you give me more details on this? I realize I can create an empty
> > tmp table to get through the parser analysis stuff, but how do I do
> > something in nodeMaterial?
>
> * ExecMaterial
> *
> * The first time this is called, ExecMaterial retrieves tuples
> * this node's outer subplan and inserts them into a temporary
> ^^^^^^^
>
> * relation. After this is done, a flag is set indicating that
> * the subplan has been materialized. Once the relation is
> * materialized, the first tuple is then returned. Successive
> * calls to ExecMaterial return successive tuples from the temp
> * relation.
>
> As you see, this node materializes some plan results into temp relation:
> instead of doing SELECT ... INTO temp FROM ... WHERE ... you could
> create Material node using plan for 'SELECT ... FROM ... WHERE ...' as
> its subplan. SeqScan of this materialized relation can be used in any
> join plans just like scan od normal relation, e.g. - NESTLOOP plan:
>
> NESTLOOP
> SeqScan A
> SeqScan B
>
> becomes
>
> NESTLOOP
> SeqScan
> Material
> ...subplan here...
> SeqScan B (or other Material)
>
> and so on...
The problem now is that I don't understand much about what happens
inside the optimizer or executor. I am sure you are correct that we can
have the subselect as a subnode, and if you think that is best, then it
is.
This pretty much stops me in developing subselects. I have the concepts
down of what has to happen, but I can not implement it. It will take me
several months to learn how the optimizer and executor work in enough
detail to implement this.
I usually alot 2-3 days a month for PostgreSQL development.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Thu Oct 30 01:30:59 1997
Received: from renoir.op.net (root@renoir.op.net [206.84.208.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA17986
for <maillist@candle.pha.pa.us>; Thu, 30 Oct 1997 01:30:58 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA27090 for <maillist@candle.pha.pa.us>; Thu, 30 Oct 1997 01:19:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id BAA28901; Thu, 30 Oct 1997 01:16:38 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 30 Oct 1997 01:16:17 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id BAA28673 for pgsql-hackers-outgoing; Thu, 30 Oct 1997 01:16:10 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.5/8.7.5) with ESMTP id BAA27557 for <hackers@postgreSQL.org>; Thu, 30 Oct 1997 01:15:27 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by www.krasnet.ru (8.8.7/8.7.3) with SMTP id NAA20275; Thu, 30 Oct 1997 13:16:10 +0700 (KRS)
From: "Vadim B. Mikheev" <vadim@sable.krasnoyarsk.su>
Organization: ITTS (Krasnoyarsk)
X-Mailer: Mozilla 3.01 (X11; I; FreeBSD 2.2.5-RELEASE i386)
MIME-Version: 1.0
To: PostgreSQL Developers List <hackers@postgreSQL.org>
Subject: [HACKERS] Subqueries?
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@hub.org
Precedence: bulk
Status: OR
Hi!
Bruce, did you begin with them ?
I agreed that subqueries should be implemented like SQL-funcs, but
I would suggest to don't CREATE FUNCTION - this is quite bad for
performance, but use some new node (VirtualFunc or SubQuery or) and
handle such nodes like sql-funcs are handled in function.c
(but without parser/planner invocation on each call - should be
fixed!). Also, not corelated subqueries returning single result
can't be replaced in parser/planner by constant node: rules (and so -
views), spi and PL use _prepared_ plans...
It seems that this is not hard work...
Vadim
From owner-pgsql-hackers@hub.org Thu Oct 30 16:31:59 1997
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id QAA07360
for <maillist@candle.pha.pa.us>; Thu, 30 Oct 1997 16:31:49 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.5/8.7.5) with SMTP id QAA11483; Thu, 30 Oct 1997 16:27:11 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 30 Oct 1997 16:26:14 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.5/8.7.5) id QAA11163 for pgsql-hackers-outgoing; Thu, 30 Oct 1997 16:26:07 -0500 (EST)
Received: from candle.pha.pa.us (root@s3-03.ppp.op.net [206.84.210.195]) by hub.org (8.8.5/8.7.5) with ESMTP id QAA10874 for <hackers@postgreSQL.org>; Thu, 30 Oct 1997 16:25:12 -0500 (EST)
> int linkType (IN, NOTIN, ANY, EXISTS, OPERATOR...)
> Oid operator /* subquery must return single row */
> List *lefthand; /* parent stuff */
> Node *subquery; /* represents nodes from parser */
> Index Subindex; /* filled in to index Query->subqueries */
Ok, I agreed that it's better to have new node and don't put subquery stuff
into Expr node.
int linkType
is one of EXISTS, ANY, ALL, EXPR. EXPR is for the case of expression
subqueries (following Sybase naming) which must return single row -
(a, b, c) = (subquery).
Note again, that there are no linkType for IN and NOTIN here.
User' IN and NOT IN must be converted to = ANY and <> ALL by parser.
We need not in Oid operator! In all cases we need in
List *oper
list of Oper nodes for each of a, b, c, ... and operator (=, ...)
corresponding to data type of a, b, c, ...
List *lefthand
is list of Var/Const nodes - representation of (a, b, c, ...)
What is Node *subquery ?
In optimizer we need either in Subindex (to get subquery from Query->subqueries
when beeing in Sublink) or in Node *subquery inside Sublink itself.
BTW, after some thought I don't see how Query->subqueries will be usefull.
So, may be just add bool hassubqueries to Query (and Query *parentQuery)
and use Query *subquery in Sublink, but not subindex ?
>
> Also, when parsing the subqueries, we need to keep track of correlated
> references. I recommend we add a field to the Var structure:
>
> Index sublevel; /* range table reference:
> = 0 current level of query
> < 0 parent above this many levels
> > 0 index into subquery list
> */
>
> This way, a Var node with sublevel 0 is the current level, and is true
> in most cases. This helps us not have to change much code. sublevel =
> -1 means it references the range table in the parent query. sublevel =
> -2 means the parent's parent. sublevel = 2 means it references the range
> table of the second entry in Query->subqueries. Varno and varattno are
> still meaningful. Of course, we can't reference variables in the
> subqueries from the parent in the parser code, but Vadim may want to.
^^^^^^^^^^^^^^^^^
No. So, just use sublevel >= 0: 0 - current level, 1 - one level up, ...
sublevel is for optimizer only - executor will not use it.
>
> When doing a Var lookup in the parser, we look in the current level
> first, but if not found, if it is a subquery, we can look at the parent
> and parent's parent to set the sublevel, varno, and varatno properly.
>
> We create no phantom range table entries in the subquery, and no phantom
> target list entries. We can leave that all for the upper optimizer.
Ok.
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 12 08:06:41 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id IAA00786
for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 08:06:39 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id EAA12270 for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 04:16:10 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA08460;
> btw, to implement "(a,b,c) OP (d,e,f)" I made a new routine in the parser called
> makeRowExpr() which breaks this up into a sequence of "and" and/or "or" expressions.
> If lists are handled farther back, this routine should move to there also and the
> parser will just pass the lists. Note that some assumptions have to be made about the
> meaning of "(a,b) OP (c,d)", since usually we only have knowledge of the behavior of
> "a OP c". Easy for the standard SQL operators, unknown for others, but maybe it is OK
> to disallow those cases or to look for specific appearance of the operator to guess
> the behavior (e.g. if the operator has "<" or "=" or ">" then build as "and"s and if
> it has "<>" or "!" then build as "or"s.
Oh, god! I never thought about this!
Ok, I have to agree:
1. Only <, <=, =, >, >=, <> is allowed with subselects
2. Use OR's for <>, and so - we need in bool useor in SubLink
for <>, <> ANY and <> ALL:
typedef struct SubLink {
NodeTag type;
int linkType; /* EXISTS, ALL, ANY, EXPR */
bool useor; /* TRUE for <> */
List *lefthand; /* List of Var/Const nodes on the left */
List *oper; /* List of Oper nodes */
Query *subquery; /* */
} SubLink;
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 12 08:06:53 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id IAA00814
for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 08:06:51 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id EAA12449 for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 04:26:03 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id EAA01671; Mon, 12 Jan 1998 04:17:59 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 12 Jan 1998 04:17:29 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id EAA01651 for pgsql-hackers-outgoing; Mon, 12 Jan 1998 04:17:23 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.8/8.7.5) with ESMTP id EAA01633 for <hackers@postgresql.org>; Mon, 12 Jan 1998 04:16:44 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA08460;
> btw, to implement "(a,b,c) OP (d,e,f)" I made a new routine in the parser called
> makeRowExpr() which breaks this up into a sequence of "and" and/or "or" expressions.
> If lists are handled farther back, this routine should move to there also and the
> parser will just pass the lists. Note that some assumptions have to be made about the
> meaning of "(a,b) OP (c,d)", since usually we only have knowledge of the behavior of
> "a OP c". Easy for the standard SQL operators, unknown for others, but maybe it is OK
> to disallow those cases or to look for specific appearance of the operator to guess
> the behavior (e.g. if the operator has "<" or "=" or ">" then build as "and"s and if
> it has "<>" or "!" then build as "or"s.
Oh, god! I never thought about this!
Ok, I have to agree:
1. Only <, <=, =, >, >=, <> is allowed with subselects
2. Use OR's for <>, and so - we need in bool useor in SubLink
for <>, <> ANY and <> ALL:
typedef struct SubLink {
NodeTag type;
int linkType; /* EXISTS, ALL, ANY, EXPR */
bool useor; /* TRUE for <> */
List *lefthand; /* List of Var/Const nodes on the left */
List *oper; /* List of Oper nodes */
Query *subquery; /* */
} SubLink;
Vadim
From vadim@sable.krasnoyarsk.su Mon Jan 12 08:06:38 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id IAA00783
for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 08:06:36 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id EAA12377 for <maillist@candle.pha.pa.us>; Mon, 12 Jan 1998 04:21:55 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA08470;
> btw, to implement "(a,b,c) OP (d,e,f)" I made a new routine in the parser called
> makeRowExpr() which breaks this up into a sequence of "and" and/or "or" expressions.
> If lists are handled farther back, this routine should move to there also and the
> parser will just pass the lists. Note that some assumptions have to be made about the
> meaning of "(a,b) OP (c,d)", since usually we only have knowledge of the behavior of
> "a OP c". Easy for the standard SQL operators, unknown for others, but maybe it is OK
> to disallow those cases or to look for specific appearance of the operator to guess
> the behavior (e.g. if the operator has "<" or "=" or ">" then build as "and"s and if
> it has "<>" or "!" then build as "or"s.
Sorry, I forgot something: is (a, b) OP (x, y) in standard ?
If not then I suggest to don't implement it at all and allow
(a, b) OP [ANY|ALL] (subselect) only.
Vadim
From vadim@sable.krasnoyarsk.su Tue Jan 13 09:30:58 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id JAA28551
for <maillist@candle.pha.pa.us>; Tue, 13 Jan 1998 09:30:56 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id JAA26483 for <maillist@candle.pha.pa.us>; Tue, 13 Jan 1998 09:21:36 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id VAA04356;
Ok. I don't see how Query->subqueries could me help, but I foresee
that Query->sublinks can do it. Could you add this ?
Bruce Momjian wrote:
>
> >
> > What is Node *subquery ?
> > In optimizer we need either in Subindex (to get subquery from Query->subqueries
> > when beeing in Sublink) or in Node *subquery inside Sublink itself.
> > BTW, after some thought I don't see how Query->subqueries will be usefull.
> > So, may be just add bool hassubqueries to Query (and Query *parentQuery)
> > and use Query *subquery in Sublink, but not subindex ?
>
> OK, I originally created it because the parser would have trouble
> filling in a List* field in SelectStmt while it was parsing a WHERE
> clause. I decided to just stick the SelectStmt* into Sublink->subquery.
>
> While we are going through the parse output to fill in the Query*, I
> thought we should move the actual subquery parse output to a separate
> place, and once the Query* was completed, spin through the saved
> subquery parse list and stuff Query->subqueries with a list of Query*
> for the subqueries. I thought this would be easier, because we would
> then have all the subqueries in a nice list that we can manage easier.
>
> In fact, we can fill Query->subqueries with SelectStmt* as we process
> the WHERE clause, then convert them to Query* at the end.
>
> If you would rather keep the subquery Query* entries in the Sublink
> structure, we can do that. The only issue I see is that when you want
> to get to them, you have to wade through the WHERE clause to find them.
> For example, we will have to run the subquery Query* through the rewrite
> system. Right now, for UNION, I have a nice union List* in Query, and I
> just spin through it in postgres.c for each Union query. If we keep the
> subquery Query* inside Sublink, we have to have some logic to go through
> and find them.
>
> If we just have an Index in Sublink to the Query->subqueries, we can use
> the nth() macro to find them quite easily.
>
> But it is up to you. I really don't know how you are going to handle
> things like:
>
> select *
> from taba
> where x = 3 and y = 5 and (z=6 or q in (select g from tabb ))
No problems.
>
> My logic was to break the problem down to single queries as much as
> possible, so we would be breaking the problem up into pieces. Whatever
> is easier for you.
Vadim
From owner-pgsql-hackers@hub.org Tue Jan 13 10:32:35 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA29523
for <maillist@candle.pha.pa.us>; Tue, 13 Jan 1998 10:32:33 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id KAA03743; Tue, 13 Jan 1998 10:32:13 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Tue, 13 Jan 1998 10:31:57 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id KAA03708 for pgsql-hackers-outgoing; Tue, 13 Jan 1998 10:31:51 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id KAA03628 for <hackers@postgreSQL.org>; Tue, 13 Jan 1998 10:31:20 -0500 (EST)
In-Reply-To: <34BB7829.2B18D4B5@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 13, 98 09:20:25 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
>
> Ok. I don't see how Query->subqueries could me help, but I foresee
> that Query->sublinks can do it. Could you add this ?
OK, so instead of moving the query out of the SubLink structure, you
want the Query* in the Sublink structure, and a List* of SubLink
pointers in the query structure?
Query
{
...
List *sublink; /* list of pointers to Sublinks
...
}
I can do that. Let me know.
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Tue Jan 13 22:23:46 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id WAA08806
for <maillist@candle.pha.pa.us>; Tue, 13 Jan 1998 22:23:45 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id WAA11486 for <maillist@candle.pha.pa.us>; Tue, 13 Jan 1998 22:09:55 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id KAA05660;
> > Ok. I don't see how Query->subqueries could me help, but I foresee
> > that Query->sublinks can do it. Could you add this ?
>
> OK, so instead of moving the query out of the SubLink structure, you
> want the Query* in the Sublink structure, and a List* of SubLink
> pointers in the query structure?
Yes.
>
> Query
> {
> ...
> List *sublink; /* list of pointers to Sublinks
> ...
> }
>
> I can do that. Let me know.
Thanks!
Are there any opened issues ?
Vadim
From owner-pgsql-hackers@hub.org Thu Jan 15 19:00:40 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id TAA21676
for <maillist@candle.pha.pa.us>; Thu, 15 Jan 1998 19:00:39 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id SAA23948 for <maillist@candle.pha.pa.us>; Thu, 15 Jan 1998 18:35:59 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id SAA27814; Thu, 15 Jan 1998 18:32:40 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 15 Jan 1998 18:32:20 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id SAA27668 for pgsql-hackers-outgoing; Thu, 15 Jan 1998 18:32:08 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id SAA27425 for <hackers@postgreSQL.org>; Thu, 15 Jan 1998 18:31:32 -0500 (EST)
In-Reply-To: <34BC2C4E.83E92D82@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 14, 98 10:09:02 am
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
>
> Bruce Momjian wrote:
> >
> > >
> > > Ok. I don't see how Query->subqueries could me help, but I foresee
> > > that Query->sublinks can do it. Could you add this ?
> >
> > OK, so instead of moving the query out of the SubLink structure, you
> > want the Query* in the Sublink structure, and a List* of SubLink
> > pointers in the query structure?
>
> Yes.
>
> >
> > Query
> > {
> > ...
> > List *sublink; /* list of pointers to Sublinks
> > ...
> > }
> >
> > I can do that. Let me know.
>
> Thanks!
>
> Are there any opened issues ?
OK, what do you need me to do. Do you want me to create the Sublink
support stuff, fill them in in the parser, and pass them through the
rewrite section and into the optimizer. I will prepare a list of
changes.
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Thu Jan 15 19:00:38 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id TAA21663
for <maillist@candle.pha.pa.us>; Thu, 15 Jan 1998 19:00:36 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id SAA23925 for <maillist@candle.pha.pa.us>; Thu, 15 Jan 1998 18:35:42 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id SAA27796; Thu, 15 Jan 1998 18:32:37 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Thu, 15 Jan 1998 18:31:52 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id SAA27463 for pgsql-hackers-outgoing; Thu, 15 Jan 1998 18:31:37 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id SAA27167 for <hackers@postgreSQL.org>; Thu, 15 Jan 1998 18:31:06 -0500 (EST)
In-Reply-To: <34B9E3B5.CF9AC8E3@sable.krasnoyarsk.su> from "Vadim B. Mikheev" at Jan 12, 98 04:34:45 pm
X-Mailer: ELM [version 2.4 PL25]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> typedef struct SubLink {
> NodeTag type;
> int linkType; /* EXISTS, ALL, ANY, EXPR */
> bool useor; /* TRUE for <> */
> List *lefthand; /* List of Var/Const nodes on the left */
> List *oper; /* List of Oper nodes */
> Query *subquery; /* */
> } SubLink;
OK, we add this structure above. During parsing, *subquery actually
will hold Node *parsetree, not Query *.
And add to Query:
bool hasSubLinks;
Also need a function to return a List* of SubLink*. I just did a
similar thing with Aggreg*. And Var gets:
int uplevels;
Is that it?
--
Bruce Momjian
maillist@candle.pha.pa.us
From owner-pgsql-hackers@hub.org Fri Jan 16 04:36:05 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA09604
for <maillist@candle.pha.pa.us>; Fri, 16 Jan 1998 04:36:03 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id EAA07040; Fri, 16 Jan 1998 04:35:27 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Fri, 16 Jan 1998 04:35:18 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id EAA06936 for pgsql-hackers-outgoing; Fri, 16 Jan 1998 04:35:13 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.8/8.7.5) with ESMTP id EAA06823 for <hackers@postgreSQL.org>; Fri, 16 Jan 1998 04:34:22 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id QAA10384;
> OK, what do you need me to do. Do you want me to create the Sublink
> support stuff, fill them in in the parser, and pass them through the
> rewrite section and into the optimizer. I will prepare a list of
> changes.
Please do this. I'm ready to start coding of things in optimizer.
Vadim
From vadim@sable.krasnoyarsk.su Sun Jan 18 07:32:52 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id HAA14786
for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 07:32:51 -0500 (EST)
Received: from www.krasnet.ru ([193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id HAA29385 for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 07:25:55 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id TAA15780;
> > OK, I have created the SubLink structure with supporting routines, and
> > have added code to create the SubLink structures in the parser, and have
> > added Query->hasSubLink.
> >
> > I changed gram.y to support:
> >
> > (x,y,z) OP (subselect)
> >
> > where OP is any operator. Is that right, or are we doing only certain
> > ones, and of so, do we limit it in the parser?
>
> Seems like we would want to pass most operators and expressions through
> gram.y, and then call elog() in either the transformation or in the
> optimizer if it is an operator which can't be supported.
Not in optimizer, in parser, please.
Remember that for <> SubLink->useor must be TRUE and this is parser work
(optimizer don't know about "=", "<>", etc but only about Oper nodes).
IN ("=" ANY) and NOT IN ("<>" ALL) transformations are also parser work.
Vadim
From owner-pgsql-hackers@hub.org Sun Jan 18 21:08:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id VAA00825
for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 21:08:57 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id TAA25254 for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 19:18:24 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id TAA06912; Sun, 18 Jan 1998 19:17:01 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Sun, 18 Jan 1998 19:11:05 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id TAA06322 for pgsql-hackers-outgoing; Sun, 18 Jan 1998 19:11:01 -0500 (EST)
Received: from clio.trends.ca (root@clio.trends.ca [209.47.148.2]) by hub.org (8.8.8/8.7.5) with ESMTP id TAA06144 for <hackers@postgresql.org>; Sun, 18 Jan 1998 19:10:31 -0500 (EST)
Received: from www.krasnet.ru ([193.125.44.86])
by clio.trends.ca (8.8.8/8.8.8) with ESMTP id HAA12383
for <hackers@postgreSQL.org>; Sun, 18 Jan 1998 07:28:38 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id TAA15780;
> > OK, I have created the SubLink structure with supporting routines, and
> > have added code to create the SubLink structures in the parser, and have
> > added Query->hasSubLink.
> >
> > I changed gram.y to support:
> >
> > (x,y,z) OP (subselect)
> >
> > where OP is any operator. Is that right, or are we doing only certain
> > ones, and of so, do we limit it in the parser?
>
> Seems like we would want to pass most operators and expressions through
> gram.y, and then call elog() in either the transformation or in the
> optimizer if it is an operator which can't be supported.
Not in optimizer, in parser, please.
Remember that for <> SubLink->useor must be TRUE and this is parser work
(optimizer don't know about "=", "<>", etc but only about Oper nodes).
IN ("=" ANY) and NOT IN ("<>" ALL) transformations are also parser work.
Vadim
From vadim@sable.krasnoyarsk.su Sun Jan 18 23:59:08 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id XAA10497
for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 23:59:07 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id XAA06941 for <maillist@candle.pha.pa.us>; Sun, 18 Jan 1998 23:44:32 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id LAA16745
for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 11:46:28 +0700 (KRS)
> In SubLink->oper, do you want the oid of the pg_operator, or the oid of
> the pg_proc assigned to the operator?
>
> Currently, I am giving you the oid of pg_operator.
No! I need in Oper nodes here. For "normal" operators parser
returns Expr node with opType = OP_EXPR and corresponding Oper
in Node *oper. Near the same for SubLink: I need in Oper node
for each pair of Var/Const from the left side and target entry from
the subquery.
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 19 01:02:23 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA24036
for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 01:02:21 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id BAA13913; Mon, 19 Jan 1998 01:02:16 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 19 Jan 1998 01:01:41 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id BAA13824 for pgsql-hackers-outgoing; Mon, 19 Jan 1998 01:01:34 -0500 (EST)
Received: from candle.pha.pa.us (root@s5-03.ppp.op.net [209.152.195.67]) by hub.org (8.8.8/8.7.5) with ESMTP id BAA13699 for <hackers@postgreSQL.org>; Mon, 19 Jan 1998 01:00:59 -0500 (EST)
OK, I have added code to allow the SubLinks make it to the optimizer.
I implemented ParseState->parentParseState, but not parentQuery, because
the parentParseState is much more valuable to me, and Vadim thought it
might be useful, but was not positive. Also, keeping that parentQuery
pointer valid through rewrite may be difficult, so I dropped it.
ParseState is only valid in the parser.
I have not done:
correlated subquery column references
added Var->sublevels_up
gotten this to work in the rewrite system
have not added full CopyNode support
I will address these in the next few days.
--
Bruce Momjian
maillist@candle.pha.pa.us
From vadim@sable.krasnoyarsk.su Mon Jan 19 01:32:54 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA24335
for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 01:32:52 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id BAA10610 for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 01:23:02 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id NAA16879
for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 13:25:28 +0700 (KRS)
> OK, I have added code to allow the SubLinks make it to the optimizer.
>
> I implemented ParseState->parentParseState, but not parentQuery, because
> the parentParseState is much more valuable to me, and Vadim thought it
> might be useful, but was not positive. Also, keeping that parentQuery
> pointer valid through rewrite may be difficult, so I dropped it.
> ParseState is only valid in the parser.
>
> I have not done:
>
> correlated subquery column references
> added Var->sublevels_up
> gotten this to work in the rewrite system
> have not added full CopyNode support
>
> I will address these in the next few days.
Nice! I'm starting with non-correlated subqueries...
Vadim
From owner-pgsql-hackers@hub.org Mon Jan 19 01:35:50 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id BAA24362
for <maillist@candle.pha.pa.us>; Mon, 19 Jan 1998 01:35:48 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id BAA17531; Mon, 19 Jan 1998 01:35:39 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Mon, 19 Jan 1998 01:35:33 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id BAA17460 for pgsql-hackers-outgoing; Mon, 19 Jan 1998 01:35:28 -0500 (EST)
Received: from www.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.8/8.7.5) with ESMTP id BAA17323 for <hackers@postgreSQL.org>; Mon, 19 Jan 1998 01:35:03 -0500 (EST)
Received: from sable.krasnoyarsk.su (www.krasnet.ru [193.125.44.86])
by www.krasnet.ru (8.8.7/8.8.7) with ESMTP id NAA16904;
> OK, I have added code to allow the SubLinks make it to the optimizer.
>
> I implemented ParseState->parentParseState, but not parentQuery, because
> the parentParseState is much more valuable to me, and Vadim thought it
> might be useful, but was not positive. Also, keeping that parentQuery
> pointer valid through rewrite may be difficult, so I dropped it.
> ParseState is only valid in the parser.
>
> I have not done:
>
> correlated subquery column references
> added Var->sublevels_up
> gotten this to work in the rewrite system
> have not added full CopyNode support
>
> I will address these in the next few days.
Nice! I'm starting with non-correlated subqueries...
Vadim
From owner-pgsql-hackers@hub.org Wed Jan 21 04:00:59 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id EAA14981
for <maillist@candle.pha.pa.us>; Wed, 21 Jan 1998 04:00:56 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id DAA02432 for <maillist@candle.pha.pa.us>; Wed, 21 Jan 1998 03:46:22 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id DAA12583; Wed, 21 Jan 1998 03:45:43 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Wed, 21 Jan 1998 03:44:07 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id DAA12288 for pgsql-hackers-outgoing; Wed, 21 Jan 1998 03:44:02 -0500 (EST)
Received: from gandalf.sd.spardat.at (gandalf.telecom.at [194.118.26.84]) by hub.org (8.8.8/8.7.5) with ESMTP id DAA12263 for <pgsql-hackers@hub.org>; Wed, 21 Jan 1998 03:43:18 -0500 (EST)
Received: from sdgtw.sd.spardat.at (sdgtw.sd.spardat.at [172.18.99.31])
by gandalf.sd.spardat.at (8.8.8/8.8.8) with ESMTP id JAA38408
for <pgsql-hackers@hub.org>; Wed, 21 Jan 1998 09:42:55 +0100
Received: by sdgtw.sd.spardat.at with Internet Mail Service (5.0.1458.49)
From: Zeugswetter Andreas DBT <Andreas.Zeugswetter@telecom.at>
To: "'pgsql-hackers@hub.org'" <pgsql-hackers@hub.org>
Subject: [HACKERS] Re: subselects
Date: Wed, 21 Jan 1998 09:42:52 +0100
X-Priority: 3
MIME-Version: 1.0
X-Mailer: Internet Mail Service (5.0.1458.49)
Content-Type: text/plain
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
Bruce wrote:
> I have completed adding Var.varlevelsup, and have added code to the
> parser to properly set the field. It will allow correlated references
> in the WHERE clause, but not in the target list.
select i2.ip1, i1.ip4 from nameip i1 where ip1 = (select ip1 from nameip
i2);
522: Table (i2) not selected in query.
select i1.ip4 from nameip i1 where ip1 = (select i1.ip1 from nameip i2);
284: A subquery has returned not exactly one row.
select i1.ip4 from nameip i1 where ip1 = (select i1.ip1 from nameip i2
where name='zeus');
2 row(s) retrieved.
Informix allows correlated references in the target list. It also allows
subselects in the target list as in:
select i1.ip4, (select i1.ip1 from nameip i2) from nameip i1;
284: A subquery has returned not exactly one row.
select i1.ip4, (select i1.ip1 from nameip i2 where name='zeus') from
nameip i1;
2 row(s) retrieved.
Is this what you were looking for ?
Andreas
From owner-pgsql-hackers@hub.org Wed Jan 21 05:31:02 1998
Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id FAA15884
for <maillist@candle.pha.pa.us>; Wed, 21 Jan 1998 05:31:01 -0500 (EST)
Received: from hub.org (hub.org [209.47.148.200]) by renoir.op.net (o1/$ Revision: 1.14 $) with ESMTP id FAA04709 for <maillist@candle.pha.pa.us>; Wed, 21 Jan 1998 05:16:16 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id FAA05191; Wed, 21 Jan 1998 05:15:42 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Wed, 21 Jan 1998 05:14:02 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id FAA04951 for pgsql-hackers-outgoing; Wed, 21 Jan 1998 05:13:57 -0500 (EST)
Received: from dune.krasnet.ru (www.krasnet.ru [193.125.44.86]) by hub.org (8.8.8/8.7.5) with ESMTP id FAA04610 for <hackers@postgreSQL.org>; Wed, 21 Jan 1998 05:12:18 -0500 (EST)
Received: from sable.krasnoyarsk.su (dune.krasnet.ru [193.125.44.86])
by dune.krasnet.ru (8.8.7/8.8.7) with ESMTP id RAA01918;
> We are only going to have subselects in the WHERE clause, not in the
> target list, right?
>
> The standard says we can have them either place, but I didn't think we
> were implementing the target list subselects.
>
> Is that correct?
Yes, this is right for 6.3. I hope that we'll support subselects in
target list, FROM, etc in future.
BTW, I'm going to implement subselect in (let's say) "natural" way -
without substitution of parent query relations into subselect and so on,
but by execution of (correlated) subqueries for each upper query row
(may be with cacheing of results in hash table for better performance).
Sure, this is much more clean way and much more clear how to do this.
This seems like SQL-func way, but funcs start/run/stop Executor each time
when called and this breaks performance.
Vadim
From owner-pgsql-hackers@hub.org Wed Jan 21 10:02:02 1998
Received: from hub.org (hub.org [209.47.148.200])
by candle.pha.pa.us (8.8.5/8.8.5) with ESMTP id KAA20456
for <maillist@candle.pha.pa.us>; Wed, 21 Jan 1998 10:02:01 -0500 (EST)
Received: from localhost (majordom@localhost) by hub.org (8.8.8/8.7.5) with SMTP id KAA06778; Wed, 21 Jan 1998 10:02:13 -0500 (EST)
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Wed, 21 Jan 1998 10:00:41 -0500 (EST)
Received: (from majordom@localhost) by hub.org (8.8.8/8.7.5) id KAA06544 for pgsql-hackers-outgoing; Wed, 21 Jan 1998 10:00:37 -0500 (EST)
Received: from u1.abs.net (root@u1.abs.net [207.114.0.131]) by hub.org (8.8.8/8.7.5) with ESMTP id KAA06326 for <pgsql-hackers@postgresql.org>; Wed, 21 Jan 1998 10:00:03 -0500 (EST)
Received: from insightdist.com (nobody@localhost)
by u1.abs.net (8.8.5/8.8.5) with UUCP id JAA08009
for pgsql-hackers@postgresql.org; Wed, 21 Jan 1998 09:40:29 -0500 (EST)
X-Authentication-Warning: u1.abs.net: nobody set sender to insightdist.com!darrenk using -f
Received: by insightdist.com (AIX 3.2/UCB 5.64/4.03)
id AA33174; Wed, 21 Jan 1998 09:26:09 -0500
Received: by ceodev (AIX 4.1/UCB 5.64/4.03)
id AA36452; Wed, 21 Jan 1998 09:13:05 -0500
Date: Wed, 21 Jan 1998 09:13:05 -0500
From: darrenk@insightdist.com (Darren King)
Message-Id: <9801211413.AA36452@ceodev>
To: pgsql-hackers@postgreSQL.org
Subject: Re: [HACKERS] subselects
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Md5: 4wI6dUsUAXei+yg3JycjGw==
Sender: owner-pgsql-hackers@hub.org
Precedence: bulk
Status: OR
> We are only going to have subselects in the WHERE clause, not in the
> target list, right?
>
> The standard says we can have them either place, but I didn't think we
> were implementing the target list subselects.
>
> Is that correct?
What about the HAVING clause? Currently not in, but someone here wants
to take a stab at it.
Doesn't seem that tough...loops over the tuples returned from the group
by node and checks the expression such as "x > 5" or "x = (subselect)".
The cost analysis in the optimizer could be tricky come to think of it.
If a subselect has a HAVING, would have to have a formula to determine
