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Update TODO list.

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Bruce Momjian 1999-09-27 17:05:08 +00:00
parent 74a263ed34
commit 99fb237da2
2 changed files with 78 additions and 1 deletions
doc
TODO
TODO.detail
subquery

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doc/TODO

@ -1,6 +1,6 @@
TODO list for PostgreSQL
========================
Last updated: Mon Sep 27 11:20:02 EDT 1999
Last updated: Mon Sep 27 13:02:57 EDT 1999
Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
@ -250,6 +250,7 @@ MISC
* Make oid use oidin/oidout not int4in/int4out in pg_type.h
* Improve Subplan list handling
* Allow Subplans to use efficient joins(hash, merge) with upper variable
[subquery]
* use fmgr_info()/fmgr_faddr() instead of fmgr() calls in high-traffic
places, like GROUP BY, UNIQUE, index processing, etc.
* improve dynamic memory allocation by introducing tuple-context memory

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From vadim@krs.ru Fri Aug 6 00:02:02 1999
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Date: Fri, 06 Aug 1999 12:01:57 +0800
From: Vadim Mikheev <vadim@krs.ru>
Organization: OJSC Rostelecom (Krasnoyarsk)
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To: Bruce Momjian <maillist@candle.pha.pa.us>
CC: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgreSQL.org
Subject: Re: [HACKERS] Idea for speeding up uncorrelated subqueries
References: <199908060331.XAA22277@candle.pha.pa.us>
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Status: RO
Bruce Momjian wrote:
>
> Isn't it something that takes only a few hours to implement. We can't
> keep telling people to us EXISTS, especially because most SQL people
> think correlated queries are slower that non-correlated ones. Can we
> just on-the-fly rewrite the query to use exists?
This seems easy to implement. We could look does subquery have
aggregates or not before calling union_planner() in
subselect.c:_make_subplan() and rewrite it (change
slink->subLinkType from IN to EXISTS and add quals).
Without caching implemented IN-->EXISTS rewriting always
has sence.
After implementation of caching we probably should call union_planner()
for both original/modified subqueries and compare costs/sizes
of EXISTS/IN_with_caching plans and maybe even make
decision what plan to use after parent query is planned
and we know for how many parent rows subplan will be executed.
Vadim
From tgl@sss.pgh.pa.us Fri Aug 6 00:15:23 1999
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To: Bruce Momjian <maillist@candle.pha.pa.us>
cc: Vadim Mikheev <vadim@krs.ru>, pgsql-hackers@postgreSQL.org
Subject: Re: [HACKERS] Idea for speeding up uncorrelated subqueries
In-reply-to: Your message of Thu, 5 Aug 1999 23:31:01 -0400 (EDT)
<199908060331.XAA22277@candle.pha.pa.us>
Date: Fri, 06 Aug 1999 00:14:50 -0400
Message-ID: <6783.933912890@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Status: RO
Bruce Momjian <maillist@candle.pha.pa.us> writes:
> Isn't it something that takes only a few hours to implement. We can't
> keep telling people to us EXISTS, especially because most SQL people
> think correlated queries are slower that non-correlated ones. Can we
> just on-the-fly rewrite the query to use exists?
I was just about to suggest exactly that. The "IN (subselect)"
notation seems to be a lot more intuitive --- at least, people
keep coming up with it --- so why not rewrite it to the EXISTS
form, if we can handle that more efficiently?
regards, tom lane