postgresql

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Andres Freund 7975c5e0a9 Allow the WAL writer to flush WAL at a reduced rate. Commit `4de82f7d7` increased the WAL flush rate, mainly to increase the likelihood that hint bits can be set quickly. More quickly set hint bits can reduce contention around the clog et al. But unfortunately the increased flush rate can have a significant negative performance impact, I have measured up to a factor of ~4. The reason for this slowdown is that if there are independent writes to the underlying devices, for example because shared buffers is a lot smaller than the hot data set, or because a checkpoint is ongoing, the fdatasync() calls force cache flushes to be emitted to the storage. This is achieved by flushing WAL only if the last flush was longer than wal_writer_delay ago, or if more than wal_writer_flush_after (new GUC) unflushed blocks are pending. Based on some tests the default for wal_writer_delay is 1MB, which seems to work well both on SSD and rotational media. To avoid negative performance impact due to `4de82f7d7` an earlier commit (`db76b1e`) made SetHintBits() more likely to succeed; preventing performance regressions in the pgbench tests I performed. Discussion: 20160118163908.GW10941@awork2.anarazel.de		2016-02-16 00:56:34 +01:00
config	Install our "missing" script where PGXS builds can find it.	2015-12-11 16:15:05 -05:00
contrib	Add missing "static" qualifier.	2016-02-12 11:20:16 -05:00
doc	Allow the WAL writer to flush WAL at a reduced rate.	2016-02-16 00:56:34 +01:00
src	Allow the WAL writer to flush WAL at a reduced rate.	2016-02-16 00:56:34 +01:00
.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
aclocal.m4	Replace our hacked version of ax_pthread.m4 with latest upstream version.	2015-07-08 20:36:06 +03:00
configure	Add support for systemd service notifications	2016-02-02 21:04:29 -05:00
configure.in	Add support for systemd service notifications	2016-02-02 21:04:29 -05:00
COPYRIGHT	Update copyright for 2016	2016-01-02 13:33:40 -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

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/.