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Tom Lane 44634e474f Allow child-relation entries to be made in ec_has_const EquivalenceClasses. 
This fixes an oversight in commit 11cad29c91,
which introduced MergeAppend plans.  Before that happened, we never
particularly cared about the sort ordering of scans of inheritance child
relations, since appending their outputs together would destroy any
ordering anyway.  But now it's important to be able to match child relation
sort orderings to those of the surrounding query.  The original coding of
add_child_rel_equivalences skipped ec_has_const EquivalenceClasses, on the
originally-correct grounds that adding child expressions to them was
useless.  The effect of this is that when a parent variable is equated to
a constant, we can't recognize that index columns on the equivalent child
variables are not sort-significant; that is, we can't recognize that a
child index on, say, (x, y) is able to generate output in "ORDER BY y"
order when there is a clause "WHERE x = constant".  Adding child
expressions to the (x, constant) EquivalenceClass fixes this, without any
downside that I can see other than a few more planner cycles expended on
such queries.

Per recent gripe from Robert McGehee.  Back-patch to 9.1 where MergeAppend
was introduced.
2012-03-02 14:29:07 -05:00
config Don't reject threaded Python on FreeBSD. 2012-02-20 16:21:28 -05:00
contrib Add const qualifiers where they are accidentally cast away 2012-02-28 12:42:08 +02:00
doc Add COLLATION FOR expression 2012-03-02 21:12:16 +02:00
src Allow child-relation entries to be made in ec_has_const EquivalenceClasses. 2012-03-02 14:29:07 -05:00
.gitignore Add gitignore for mingw/cygwin build outputs 2011-06-09 18:11:47 +02:00
aclocal.m4 Remove cvs keywords from all files. 2010-09-20 22:08:53 +02:00
configure Allow MinGW builds to use standardly-named OpenSSL libraries. 2012-02-23 15:05:08 -05:00
configure.in Allow MinGW builds to use standardly-named OpenSSL libraries. 2012-02-23 15:05:08 -05:00
COPYRIGHT Update copyright notices for year 2012. 2012-01-01 18:01:58 -05:00
GNUmakefile.in Build src/ before contrib/ in make world 2011-08-24 21:34:49 +03:00
Makefile Allow make check in PL directories 2011-02-15 06:52:12 +02:00
README Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
README.git Trivial typo fix. 2010-09-21 14:16:00 -04:00

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, many of which are listed here:

	http://www.postgresql.org/download

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/.