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David Rowley efdcca55a3 Make better use of the new List implementation in a couple of places 
In nodeAppend.c and nodeMergeAppend.c there were some foreach loops which
looped over the list of subplans and only performed any work if the
subplan index was found in a Bitmapset.  With the old linked list
implementation of List, this form made sense as accessing the Nth list
element was O(N).  However, thanks to 1cff1b95a we now have array-based
lists, so accessing the Nth element has become O(1).

Here we make the most of the O(1) lookups and just loop over the set
members of the Bitmapset with bms_next_member().  This performs slightly
better when a small number of the list items are in the Bitmapset.  Micro
benchmarks show that when the Bitmapset contains all or most of the list
items then the new code is ever so slightly slower.  In practice, the cost
is so small that it's drowned out by various other things such as locking
the relations belonging to each subplan, etc.

The primary goal here is to leave better code examples around which benefit
better from the new list implementation.

Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAKJS1f8ZcsLVgkF4wOfRyMYTcPgLFiUAOedFC+U2vK_aFZk-BA@mail.gmail.com
2019-07-22 19:03:12 +12:00
config Update config.guess and config.sub 2019-04-27 14:25:00 +02:00
contrib Fix inconsistencies and typos in the tree 2019-07-22 10:01:50 +09:00
doc Fix inconsistencies and typos in the tree 2019-07-22 10:01:50 +09:00
src Make better use of the new List implementation in a couple of places 2019-07-22 19:03:12 +12:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.gitattributes Add XSL stylesheet to fix up SVG files 2019-06-19 21:26:42 +02:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Fix configure's AC_CHECK_DECLS tests to work correctly with clang. 2018-11-19 12:01:47 -05:00
configure Remove support for non-ELF BSD systems 2019-07-01 23:56:20 +01:00
configure.in Remove support for non-ELF BSD systems 2019-07-01 23:56:20 +01:00
COPYRIGHT Update copyright for 2019 2019-01-02 12:44:25 -05:00
GNUmakefile.in Integrate cpluspluscheck into build system. 2019-05-31 12:36:17 -07:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
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/.