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Tom Lane d2ef7758d2 Fix constant-folding of ROW(...) IS [NOT] NULL with composite fields.
The SQL standard appears to specify that IS [NOT] NULL's tests of field
nullness are non-recursive, ie, we shouldn't consider that a composite
field with value ROW(NULL,NULL) is null for this purpose.
ExecEvalNullTest got this right, but eval_const_expressions did not,
leading to weird inconsistencies depending on whether the expression
was such that the planner could apply constant folding.

Also, adjust the docs to mention that IS [NOT] DISTINCT FROM NULL can be
used as a substitute test if a simple null check is wanted for a rowtype
argument.  That motivated reordering things so that IS [NOT] DISTINCT FROM
is described before IS [NOT] NULL.  In HEAD, I went a bit further and added
a table showing all the comparison-related predicates.

Per bug #14235.  Back-patch to all supported branches, since it's certainly
undesirable that constant-folding should change the semantics.

Report and patch by Andrew Gierth; assorted wordsmithing and revised
regression test cases by me.

Report: <20160708024746.1410.57282@wrigleys.postgresql.org>
2016-07-26 15:25:02 -04:00
config Fix configure's incorrect version tests for flex and perl. 2016-05-02 11:18:10 -04:00
contrib Make contrib regression tests safe for Danish locale. 2016-07-21 16:52:36 -04:00
doc Fix constant-folding of ROW(...) IS [NOT] NULL with composite fields. 2016-07-26 15:25:02 -04:00
src Fix constant-folding of ROW(...) IS [NOT] NULL with composite fields. 2016-07-26 15:25:02 -04:00
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.gitignore Improve speed of make check-world 2015-04-23 08:59:52 -04:00
aclocal.m4 Revert changes to pthread configure tests on REL9_5_STABLE. 2015-07-09 10:59:10 +03:00
configure Stamp 9.5.3. 2016-05-09 16:50:23 -04:00
configure.in Stamp 9.5.3. 2016-05-09 16:50:23 -04:00
COPYRIGHT Update copyright for 2016 2016-01-02 13:33:39 -05:00
GNUmakefile.in Fix distclean/maintainer-clean targets to remove top-level tmp_install dir. 2015-05-13 18:48:05 -04:00
HISTORY Improve text of stub HISTORY file. 2014-02-12 18:16:17 -05:00
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README
README.git

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.  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/.