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Tom Lane 4387cf956b Avoid inserting Result nodes that only compute identity projections. The planner sometimes inserts Result nodes to perform column projections (ie, arbitrary scalar calculations) above plan nodes that lack projection logic of their own. However, we did that even if the lower plan node was in fact producing the required column set already; which is a pretty common case given the popularity of "SELECT * FROM ...". Measurements show that the useless plan node adds non-negligible overhead, especially when there are many columns in the result. So add a check to avoid inserting a Result node unless there's something useful for it to do. There are a couple of remaining places where unnecessary Result nodes could get inserted, but they are (a) much less performance-critical, and (b) coded in such a way that it's hard to avoid inserting a Result, because the desired tlist is changed on-the-fly in subsequent logic. We'll leave those alone for now. Kyotaro Horiguchi; reviewed and further hacked on by Amit Kapila and Tom Lane.		2013-03-14 13:43:18 -04:00
config	Improve handling of ereport(ERROR) and elog(ERROR).	2013-01-13 18:40:09 -05:00
contrib	Introduce less-bogus handling of collations in contrib/postgres_fdw.	2013-03-13 19:46:31 -04:00
doc	Fix documentation oversight.	2013-03-12 19:06:43 -04:00
src	Avoid inserting Result nodes that only compute identity projections.	2013-03-14 13:43:18 -04:00
.gitignore	Gitignore vcxproj files.	2013-01-23 03:44:37 -05:00
COPYRIGHT	Update copyrights for 2013	2013-01-01 17:15:01 -05:00
GNUmakefile.in	Make init-po and update-po recursive make targets	2012-06-29 14:01:54 +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
aclocal.m4	Remove cvs keywords from all files.	2010-09-20 22:08:53 +02:00
configure	Improve handling of ereport(ERROR) and elog(ERROR).	2013-01-13 18:40:09 -05:00
configure.in	Improve handling of ereport(ERROR) and elog(ERROR).	2013-01-13 18:40:09 -05:00

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/.