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Tom Lane 6a6522529f Fix some planner issues found while investigating Kevin Grittner's report 
of poorer planning in 8.3 than 8.2:

1. After pushing a constant across an outer join --- ie, given
"a LEFT JOIN b ON (a.x = b.y) WHERE a.x = 42", we can deduce that b.y is
sort of equal to 42, in the sense that we needn't fetch any b rows where
it isn't 42 --- loop to see if any additional deductions can be made.
Previous releases did that by recursing, but I had mistakenly thought that
this was no longer necessary given the EquivalenceClass machinery.

2. Allow pushing constants across outer join conditions even if the
condition is outerjoin_delayed due to a lower outer join.  This is safe
as long as the condition is strict and we re-test it at the upper join.

3. Keep the outer-join clause even if we successfully push a constant
across it.  This is *necessary* in the outerjoin_delayed case, but
even in the simple case, it seems better to do this to ensure that the
join search order heuristics will consider the join as reasonable to
make.  Mark such a clause as having selectivity 1.0, though, since it's
not going to eliminate very many rows after application of the constant
condition.

4. Tweak have_relevant_eclass_joinclause to report that two relations
are joinable when they have vars that are equated to the same constant.
We won't actually generate any joinclause from such an EquivalenceClass,
but again it seems that in such a case it's a good idea to consider
the join as worth costing out.

5. Fix a bug in select_mergejoin_clauses that was exposed by these
changes: we have to reject candidate mergejoin clauses if either side was
equated to a constant, because we can't construct a canonical pathkey list
for such a clause.  This is an implementation restriction that might be
worth fixing someday, but it doesn't seem critical to get it done for 8.3.
2008-01-09 20:42:29 +00:00
config Update config.guess and config.sub 2007-11-15 20:21:05 +00:00
contrib The original patch to disallow non-passworded connections to non-superusers 2008-01-03 21:27:59 +00:00
doc Add index entry. 2008-01-09 05:27:22 +00:00
src Fix some planner issues found while investigating Kevin Grittner's report 2008-01-09 20:42:29 +00:00
aclocal.m4 Add new auto-detection of thread flags. 2004-04-23 18:15:55 +00:00
configure Stamp release 8.3RC1. 2008-01-03 21:40:12 +00:00
configure.in Stamp release 8.3RC1. 2008-01-03 21:40:12 +00:00
COPYRIGHT Update copyrights in source tree to 2008. 2008-01-01 19:46:01 +00:00
GNUmakefile.in Replace useless uses of := by = in makefiles. 2007-02-09 15:56:00 +00:00
Makefile Remove remains of old depend target. 2007-01-20 17:16:17 +00:00
README Clean up some now-obsolete references to GBorg. 2007-11-14 01:58:18 +00:00
README.CVS Some further editorializing on README.CVS. 2004-03-28 06:09:08 +00:00

README 

PostgreSQL Database Management System
=====================================
  
This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces including some of the more
common listed below:

C++ - http://thaiopensource.org/development/libpqxx/
JDBC - http://jdbc.postgresql.org
ODBC - http://odbc.postgresql.org
Perl - http://search.cpan.org/~dbdpg/
PHP - http://www.php.net
Python - http://www.initd.org/
Ruby - http://ruby.scripting.ca/postgres/

Other language binding are available from a variety of contributing
parties.

PostgreSQL also has a great number of procedural languages available,
a short, incomplete list is below:

PL/pgSQL - included in PostgreSQL source distribution
PL/Perl - included in PostgreSQL source distribution
PL/PHP - http://projects.commandprompt.com/projects/public/plphp
PL/Python - included in PostgreSQL source distribution
PL/Java - http://pgfoundry.org/projects/pljava/
PL/Tcl - included in PostgreSQL source distribution

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Changes between all PostgreSQL releases are recorded in the
file HISTORY.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
http://www.postgresql.org/download/.  For more information look at our
web site located at http://www.postgresql.org/.