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Tom Lane f3b3b8d5be Compute correct em_nullable_relids in get_eclass_for_sort_expr(). 
Bug #8591 from Claudio Freire demonstrates that get_eclass_for_sort_expr
must be able to compute valid em_nullable_relids for any new equivalence
class members it creates.  I'd worried about this in the commit message
for db9f0e1d9a, but claimed that it wasn't a
problem because multi-member ECs should already exist when it runs.  That
is transparently wrong, though, because this function is also called by
initialize_mergeclause_eclasses, which runs during deconstruct_jointree.
The example given in the bug report (which the new regression test item
is based upon) fails because the COALESCE() expression is first seen by
initialize_mergeclause_eclasses rather than process_equivalence.

Fixing this requires passing the appropriate nullable_relids set to
get_eclass_for_sort_expr, and it requires new code to compute that set
for top-level expressions such as ORDER BY, GROUP BY, etc.  We store
the top-level nullable_relids in a new field in PlannerInfo to avoid
computing it many times.  In the back branches, I've added the new
field at the end of the struct to minimize ABI breakage for planner
plugins.  There doesn't seem to be a good alternative to changing
get_eclass_for_sort_expr's API signature, though.  There probably aren't
any third-party extensions calling that function directly; moreover,
if there are, they probably need to think about what to pass for
nullable_relids anyway.

Back-patch to 9.2, like the previous patch in this area.
2013-11-15 16:46:18 -05:00
config Remove maintainer-check target, fold into normal build 2013-10-10 20:11:56 -04:00
contrib Fix whitespace issues found by git diff --check, add gitattributes 2013-11-10 14:48:29 -05:00
doc doc: Restore proper alphabetical order. 2013-11-15 08:46:12 -05:00
src Compute correct em_nullable_relids in get_eclass_for_sort_expr(). 2013-11-15 16:46:18 -05:00
.dir-locals.el Update Emacs configuration 2013-08-13 20:08:44 -04:00
.gitattributes gitattributes: Make syntax compatible with older Git versions 2013-11-12 21:58:46 -05:00
.gitignore Add *.pot to .gitignore 2013-10-19 10:56:52 -04:00
aclocal.m4 Remove cvs keywords from all files. 2010-09-20 22:08:53 +02:00
configure Get rid of use of asprintf() in favor of a more portable implementation. 2013-10-22 18:42:13 -04:00
configure.in Fix whitespace issues found by git diff --check, add gitattributes 2013-11-10 14:48:29 -05:00
COPYRIGHT Update copyrights for 2013 2013-01-01 17:15:01 -05:00
GNUmakefile.in Remove maintainer-check target, fold into normal build 2013-10-10 20:11:56 -04:00
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 Fix doc links in README file to work with new website layout 2013-11-12 12:53:32 +01:00

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/.