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Tom Lane 1b19e2c0ba Fix up handling of simple-form CASE with constant test expression. 
eval_const_expressions() can replace CaseTestExprs with constants when
the surrounding CASE's test expression is a constant.  This confuses
ruleutils.c's heuristic for deparsing simple-form CASEs, leading to
Assert failures or "unexpected CASE WHEN clause" errors.  I had put in
a hack solution for that years ago (see commit
514ce7a331 of 2006-10-01), but bug #5794
from Peter Speck shows that that solution failed to cover all cases.

Fortunately, there's a much better way, which came to me upon reflecting
that Peter's "CASE TRUE WHEN" seemed pretty redundant: we can "simplify"
the simple-form CASE to the general form of CASE, by simply omitting the
constant test expression from the rebuilt CASE construct.  This is
intuitively valid because there is no need for the executor to evaluate
the test expression at runtime; it will never be referenced, because any
CaseTestExprs that would have referenced it are now replaced by constants.
This won't save a whole lot of cycles, since evaluating a Const is pretty
cheap, but a cycle saved is a cycle earned.  In any case it beats kluging
ruleutils.c still further.  So this patch improves const-simplification
and reverts the previous change in ruleutils.c.

Back-patch to all supported branches.  The bug exists in 8.1 too, but it's
out of warranty.
2010-12-19 15:30:44 -05:00
config Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
contrib Fix erroneous parsing of tsquery input "... & !(subexpression) | ..." 2010-12-19 12:48:34 -05:00
doc Support for collecting crash dumps on Windows 2010-12-19 16:45:28 +01:00
src Fix up handling of simple-form CASE with constant test expression. 2010-12-19 15:30:44 -05:00
.gitignore Convert cvsignore to gitignore, and add .gitignore for build targets. 2010-09-22 12:57:04 +02:00
aclocal.m4 Remove cvs keywords from all files. 2010-09-20 22:08:53 +02:00
configure Fix up getopt() reset management so it works on recent mingw. 2010-12-15 23:50:41 -05:00
configure.in Fix up getopt() reset management so it works on recent mingw. 2010-12-15 23:50:41 -05:00
COPYRIGHT
GNUmakefile.in Improved parallel make support 2010-11-12 22:15:16 +02:00
Makefile
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

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/.