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Tom Lane 624e440a47 Improve the heuristic for ordering child paths of a parallel append. Commit `ab7271677` introduced code that attempts to order the child scans of a Parallel Append node in a way that will minimize execution time, based on total cost and startup cost. However, it failed to think hard about what to do when estimated costs are exactly equal; a case that's particularly likely to occur when comparing on startup cost. In such a case the ordering of the child paths would be left to the whims of qsort, an algorithm that isn't even stable. We can improve matters by applying the rule used elsewhere in the planner: if total costs are equal, sort on startup cost, and vice versa. When both cost estimates are exactly equal, rather than letting qsort do something unpredictable, sort based on the child paths' relids, which should typically result in sorting in inheritance order. (The latter provision requires inventing a qsort-style comparator for bitmapsets, but maybe we'll have use for that for other reasons in future.) This results in a few plan changes in the select_parallel test, but those all look more reasonable than before, when the actual underlying cost numbers are taken into account. Discussion: https://postgr.es/m/4944.1515446989@sss.pgh.pa.us		2018-01-09 13:07:52 -05:00
config	Try harder to detect unavailability of __builtin_mul_overflow(int64).	2017-12-17 11:52:22 -05:00
contrib	Fix new test case to not be endian-dependent.	2018-01-04 16:00:21 -05:00
doc	Improve scripting language in pgbench	2018-01-09 18:02:04 +03:00
src	Improve the heuristic for ordering child paths of a parallel append.	2018-01-09 13:07:52 -05:00
.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	Another attempt at fixing build with various OpenSSL versions	2018-01-04 19:09:27 -05:00
configure.in	Another attempt at fixing build with various OpenSSL versions	2018-01-04 19:09:27 -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/.