2
0
mirror of https://git.postgresql.org/git/postgresql.git synced 2025-03-19 20:00:51 +08:00
Tom Lane e3ffd05b02 Weaken the planner's tests for relevant joinclauses.
We should be willing to cross-join two small relations if that allows us
to use an inner indexscan on a large relation (that is, the potential
indexqual for the large table requires both smaller relations).  This
worked in simple cases but fell apart as soon as there was a join clause
to a fourth relation, because the existence of any two-relation join clause
caused the planner to not consider clauseless joins between other base
relations.  The added regression test shows an example case adapted from
a recent complaint from Benoit Delbosc.

Adjust have_relevant_joinclause, have_relevant_eclass_joinclause, and
has_relevant_eclass_joinclause to consider that a join clause mentioning
three or more relations is sufficient grounds for joining any subset of
those relations, even if we have to do so via a cartesian join.  Since such
clauses are relatively uncommon, this shouldn't affect planning speed on
typical queries; in fact it should help a bit, because the latter two
functions in particular get significantly simpler.

Although this is arguably a bug fix, I'm not going to risk back-patching
it, since it might have currently-unforeseen consequences.
2012-04-13 16:07:17 -04:00
2010-09-20 22:08:53 +02:00
2011-02-15 06:52:12 +02:00
2010-09-21 14:16:00 -04:00

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/.
Description
No description provided
Readme 387 MiB
Languages
C 85.4%
PLpgSQL 6%
Perl 4.3%
Yacc 1.2%
Meson 0.7%
Other 2.1%