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Andres Freund 391f08fd68 Fix corruption due to vacuum_defer_cleanup_age underflowing 64bit xids 
When vacuum_defer_cleanup_age is bigger than the current xid, including the
epoch, the subtraction of vacuum_defer_cleanup_age would lead to a wrapped
around xid. While that normally is not a problem, the subsequent conversion to
a 64bit xid results in a 64bit-xid very far into the future. As that xid is
used as a horizon to detect whether rows versions are old enough to be
removed, that allows removal of rows that are still visible (i.e. corruption).

If vacuum_defer_cleanup_age was never changed from the default, there is no
chance of this bug occurring.

This bug was introduced in dc7420c2c9.  A lesser version of it exists in
12-13, introduced by fb5344c969, affecting only GiST.

The 12-13 version of the issue can, in rare cases, lead to pages in a gist
index getting recycled too early, potentially causing index entries to be
found multiple times.

The fix is fairly simple - don't allow vacuum_defer_cleanup_age to retreat
further than FirstNormalTransactionId.

Patches to make similar bugs easier to find, by adding asserts to the 64bit
xid infrastructure, have been proposed, but are not suitable for backpatching.

Currently there are no tests for vacuum_defer_cleanup_age. A patch introducing
infrastructure to make writing a test easier has been posted to the list.

Reported-by: Michail Nikolaev <michail.nikolaev@gmail.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20230108002923.cyoser3ttmt63bfn@awork3.anarazel.de
Backpatch: 12-, but impact/fix is smaller for 12-13
2023-03-07 21:36:48 -08:00
config
contrib pageinspect: Fix crash with gist_page_items() 2023-03-02 14:03:08 +09:00
doc doc: Update pg_size_pretty documentation about petabytes support 2023-03-07 19:32:27 +01:00
src Fix corruption due to vacuum_defer_cleanup_age underflowing 64bit xids 2023-03-07 21:36:48 -08:00
.cirrus.yml ci: Use windows VMs instead of windows containers 2023-02-02 21:31:48 -08:00
.dir-locals.el
.editorconfig
.git-blame-ignore-revs
.gitattributes
.gitignore
aclocal.m4
configure Fix handling of SCRAM-SHA-256's channel binding with RSA-PSS certificates 2023-02-15 10:12:31 +09:00
configure.ac Fix handling of SCRAM-SHA-256's channel binding with RSA-PSS certificates 2023-02-15 10:12:31 +09:00
COPYRIGHT Update copyright for 2023 2023-01-02 15:00:37 -05:00
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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:

	https://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
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.