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5bba65de94
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Tom Lane 5bba65de94 Fix a missed case in code for "moving average" estimate of reltuples. 
It is possible for VACUUM to scan no pages at all, if the visibility map
shows that all pages are all-visible.  In this situation VACUUM has no new
information to report about the relation's tuple density, so it wasn't
changing pg_class.reltuples ... but it updated pg_class.relpages anyway.
That's wrong in general, since there is no evidence to justify changing the
density ratio reltuples/relpages, but it's particularly bad if the previous
state was relpages=reltuples=0, which means "unknown tuple density".
We just replaced "unknown" with "zero".  ANALYZE would eventually recover
from this, but it could take a lot of repetitions of ANALYZE to do so if
the relation size is much larger than the maximum number of pages ANALYZE
will scan, because of the moving-average behavior introduced by commit
b4b6923e03.

The only known situation where we could have relpages=reltuples=0 and yet
the visibility map asserts everything's visible is immediately following
a pg_upgrade.  It might be advisable for pg_upgrade to try to preserve the
relpages/reltuples statistics; but in any case this code is wrong on its
own terms, so fix it.  Per report from Sergey Koposov.

Back-patch to 8.4, where the visibility map was introduced, same as the
previous change.
2011-08-30 14:51:38 -04:00
config Improve detection of Python 3.2 installations 2011-08-18 14:43:16 +03:00
contrib Allow more include files to be compiled in their own by adding missing 2011-08-27 11:05:33 -04:00
doc Some markup cleanup to deconfuse the find_gt_lt tool 2011-08-30 20:32:49 +03:00
src Fix a missed case in code for "moving average" estimate of reltuples. 2011-08-30 14:51:38 -04:00
.gitignore Add gitignore for mingw/cygwin build outputs 2011-06-09 18:11:47 +02:00
aclocal.m4
configure Include $cc_string in the info reported by a configure run. 2011-08-28 17:14:52 -04:00
configure.in Include $cc_string in the info reported by a configure run. 2011-08-28 17:14:52 -04:00
COPYRIGHT
GNUmakefile.in Build src/ before contrib/ in make world 2011-08-24 21:34:49 +03:00
Makefile Allow make check in PL directories 2011-02-15 06:52:12 +02:00
README
README.git

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.  Changes between all PostgreSQL releases are recorded in the
file HISTORY.  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/.