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Robert Haas 7aea8e4f2d Determine whether it's safe to attempt a parallel plan for a query. 
Commit 924bcf4f16 introduced a framework
for parallel computation in PostgreSQL that makes most but not all
built-in functions safe to execute in parallel mode.  In order to have
parallel query, we'll need to be able to determine whether that query
contains functions (either built-in or user-defined) that cannot be
safely executed in parallel mode.  This requires those functions to be
labeled, so this patch introduces an infrastructure for that.  Some
functions currently labeled as safe may need to be revised depending on
how pending issues related to heavyweight locking under paralllelism
are resolved.

Parallel plans can't be used except for the case where the query will
run to completion.  If portal execution were suspended, the parallel
mode restrictions would need to remain in effect during that time, but
that might make other queries fail.  Therefore, this patch introduces
a framework that enables consideration of parallel plans only when it
is known that the plan will be run to completion.  This probably needs
some refinement; for example, at bind time, we do not know whether a
query run via the extended protocol will be execution to completion or
run with a limited fetch count.  Having the client indicate its
intentions at bind time would constitute a wire protocol break.  Some
contexts in which parallel mode would be safe are not adjusted by this
patch; the default is not to try parallel plans except from call sites
that have been updated to say that such plans are OK.

This commit doesn't introduce any parallel paths or plans; it just
provides a way to determine whether they could potentially be used.
I'm committing it on the theory that the remaining parallel sequential
scan patches will also get committed to this release, hopefully in the
not-too-distant future.

Robert Haas and Amit Kapila.  Reviewed (in earlier versions) by Noah
Misch.
 		2015-09-16 15:38:47 -04:00
config Remove support for Unix systems without the POSIX signal APIs. 2015-08-31 12:56:10 -04:00
contrib Fix error message wording in previous sslinfo commit 2015-09-08 11:10:20 -03:00
doc Determine whether it's safe to attempt a parallel plan for a query. 2015-09-16 15:38:47 -04:00
src Determine whether it's safe to attempt a parallel plan for a query. 2015-09-16 15:38:47 -04:00
.dir-locals.el emacs: Set indent-tabs-mode in perl-mode 2015-04-12 23:53:23 -04:00
.gitattributes Add functions for dealing with PGP armor header lines to pgcrypto. 2014-10-01 16:03:39 +03:00
.gitignore Add .gitignore entries for AIX-specific intermediate build artifacts. 2015-07-08 20:44:22 -04:00
COPYRIGHT Update copyright for 2015 2015-01-06 11:43:47 -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
Makefile Allow make check in PL directories 2011-02-15 06:52:12 +02:00
README Don't generate plain-text HISTORY and src/test/regress/README anymore. 2014-02-10 20:48:04 -05:00
README.git Don't generate plain-text HISTORY and src/test/regress/README anymore. 2014-02-10 20:48:04 -05:00
aclocal.m4 Replace our hacked version of ax_pthread.m4 with latest upstream version. 2015-07-08 20:36:06 +03:00
configure Remove support for Unix systems without the POSIX signal APIs. 2015-08-31 12:56:10 -04:00
configure.in Remove support for Unix systems without the POSIX signal APIs. 2015-08-31 12:56:10 -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.  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/.