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Alvaro Herrera c0db1ec260 Avoid pin scan for replay of XLOG_BTREE_VACUUM in all cases 
Replay of XLOG_BTREE_VACUUM during Hot Standby was previously thought to
require complex interlocking that matched the requirements on the
master. This required an O(N) operation that became a significant
problem with large indexes, causing replication delays of seconds or in
some cases minutes while the XLOG_BTREE_VACUUM was replayed.

This commit skips the “pin scan” that was previously required, by
observing in detail when and how it is safe to do so, with full
documentation. The pin scan is skipped only in replay; the VACUUM code
path on master is not touched here.

No tests included. Manual tests using an additional patch to view WAL records
and their timing have shown the change in WAL records and their handling has
successfully reduced replication delay.

This is a back-patch of commits 687f2cd7a0, 3e4b7d8798, b602842613
by Simon Riggs, to branches 9.4 and 9.5.  No further backpatch is
possible because this depends on catalog scans being MVCC.  I (Álvaro)
additionally updated a slight problem in the README, which explains why
this touches the 9.6 and master branches.
2016-11-17 13:31:30 -03:00
config Fix configure's incorrect version tests for flex and perl. 2016-05-02 11:18:10 -04:00
contrib Back-patch portability fixes for contrib/pageinspect/ginfuncs.c. 2016-11-04 12:37:29 -04:00
doc Fix duplication in ALTER MATERIALIZE VIEW synopsis 2016-11-14 11:14:34 -03:00
src Avoid pin scan for replay of XLOG_BTREE_VACUUM in all cases 2016-11-17 13:31:30 -03:00
.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 Improve speed of make check-world 2015-04-23 08:59:52 -04:00
aclocal.m4 Revert changes to pthread configure tests on REL9_5_STABLE. 2015-07-09 10:59:10 +03:00
configure Stamp 9.5.5. 2016-10-24 16:10:50 -04:00
configure.in Stamp 9.5.5. 2016-10-24 16:10:50 -04:00
COPYRIGHT Update copyright for 2016 2016-01-02 13:33:39 -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
Makefile
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/.