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Tom Lane b2355a29c6 Ensure that backends see up-to-date statistics for shared catalogs.
Ever since we split the statistics collector's reports into per-database
files (commit 187492b6c2), backends have been seeing stale statistics
for shared catalogs.  This is because the inquiry message only prompts the
collector to write the per-database file for the requesting backend's own
database.  Stats for shared catalogs are in a separate file for "DB 0",
which didn't get updated.

In normal operation this was partially masked by the fact that the
autovacuum launcher would send an inquiry message at least once per
autovacuum_naptime that asked for "DB 0"; so the shared-catalog stats would
never be more than a minute out of date.  However the problem becomes very
obvious with autovacuum disabled, as reported by Peter Eisentraut.

To fix, redefine the semantics of inquiry messages so that both the
specified DB and DB 0 will be dumped.  (This might seem a bit inefficient,
but we have no good way to know whether a backend's transaction will look
at shared-catalog stats, so we have to read both groups of stats whenever
we request stats.  Sending two inquiry messages would definitely not be
better.)

Back-patch to 9.3 where the bug was introduced.

Report: <56AD41AC.1030509@gmx.net>
2016-05-25 17:48:15 -04:00
config Fix configure's incorrect version tests for flex and perl. 2016-05-02 11:18:10 -04:00
contrib Ensure plan stability in contrib/btree_gist regression test. 2016-05-12 20:04:39 -04:00
doc Further improve documentation about --quote-all-identifiers switch. 2016-05-20 15:52:08 -04:00
src Ensure that backends see up-to-date statistics for shared catalogs. 2016-05-25 17:48:15 -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 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 9.5.3. 2016-05-09 16:50:23 -04:00
configure.in Stamp 9.5.3. 2016-05-09 16:50:23 -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 Improve text of stub HISTORY file. 2014-02-12 18:16:17 -05:00
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README.git

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/.