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Tom Lane 4a4e2442a7 Fix improper uses of canonicalize_qual(). 
One of the things canonicalize_qual() does is to remove constant-NULL
subexpressions of top-level AND/OR clauses.  It does that on the assumption
that what it's given is a top-level WHERE clause, so that NULL can be
treated like FALSE.  Although this is documented down inside a subroutine
of canonicalize_qual(), it wasn't mentioned in the documentation of that
function itself, and some callers hadn't gotten that memo.

Notably, commit d007a9505 caused get_relation_constraints() to apply
canonicalize_qual() to CHECK constraints.  That allowed constraint
exclusion to misoptimize situations in which a CHECK constraint had a
provably-NULL subclause, as seen in the regression test case added here,
in which a child table that should be scanned is not.  (Although this
thinko is ancient, the test case doesn't fail before 9.2, for reasons
I've not bothered to track down in detail.  There may be related cases
that do fail before that.)

More recently, commit f0e44751d added an independent bug by applying
canonicalize_qual() to index expressions, which is even sillier since
those might not even be boolean.  If they are, though, I think this
could lead to making incorrect index entries for affected index
expressions in v10.  I haven't attempted to prove that though.

To fix, add an "is_check" parameter to canonicalize_qual() to specify
whether it should assume WHERE or CHECK semantics, and make it perform
NULL-elimination accordingly.  Adjust the callers to apply the right
semantics, or remove the call entirely in cases where it's not known
that the expression has one or the other semantics.  I also removed
the call in some cases involving partition expressions, where it should
be a no-op because such expressions should be canonical already ...
and was a no-op, independently of whether it could in principle have
done something, because it was being handed the qual in implicit-AND
format which isn't what it expects.  In HEAD, add an Assert to catch
that type of mistake in future.

This represents an API break for external callers of canonicalize_qual().
While that's intentional in HEAD to make such callers think about which
case applies to them, it seems like something we probably wouldn't be
thanked for in released branches.  Hence, in released branches, the
extra parameter is added to a new function canonicalize_qual_ext(),
and canonicalize_qual() is a wrapper that retains its old behavior.

Patch by me with suggestions from Dean Rasheed.  Back-patch to all
supported branches.

Discussion: https://postgr.es/m/24475.1520635069@sss.pgh.pa.us
2018-03-11 18:10:42 -04:00
config Extend configure's __int128 test to check for a known gcc bug. 2018-01-18 11:09:44 -05:00
contrib Revert "Temporarily instrument postgres_fdw test to look for statistics changes." 2018-03-08 11:33:27 -05:00
doc Fix cross-checking of ReservedBackends/max_wal_senders/MaxConnections. 2018-03-08 11:25:26 -05:00
src Fix improper uses of canonicalize_qual(). 2018-03-11 18:10:42 -04:00
.dir-locals.el emacs: Set indent-tabs-mode in perl-mode 2015-04-12 23:53:23 -04:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Add lcov --initial 2017-09-29 08:54:34 -04:00
aclocal.m4 Make configure check for IPC::Run when --enable-tap-tests is specified. 2017-06-15 15:56:12 -04:00
configure Tests for Kerberos/GSSAPI authentication 2018-03-06 10:57:36 -05:00
configure.in Tests for Kerberos/GSSAPI authentication 2018-03-06 10:57:36 -05:00
COPYRIGHT Update copyright for 2018 2018-01-02 23:30:12 -05:00
GNUmakefile.in Have "make coverage" recurse into contrib as well 2016-09-05 18:44:36 -03:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:22 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -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:

	https://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
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.