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Andres Freund 7c38ef2a5d Fix temporary object cleanup failing due to toast access without snapshot.
When cleaning up temporary objects during process exit the cleanup could fail
with:
  FATAL: cannot fetch toast data without an active snapshot

The bug is caused by RemoveTempRelationsCallback() not setting up a
snapshot. If an object with toasted catalog data needs to be cleaned up,
init_toast_snapshot() could fail with the above error.

Most of the time however the the problem is masked due to cached catalog
snapshots being returned by GetOldestSnapshot(). But dropping an object can
cause catalog invalidations to be emitted. If no further catalog accesses are
necessary between the invalidation processing and the next toast datum
deletion, the bug becomes visible.

It's easy to miss this bug because it typically happens after clients
disconnect and the FATAL error just ends up in the log.

Luckily temporary table cleanup at the next use of the same temporary schema
or during DISCARD ALL does not have the same problem.

Fix the bug by pushing a snapshot in RemoveTempRelationsCallback(). Also add
isolation tests for temporary object cleanup, including objects with toasted
catalog data.

A future HEAD only commit will add an assertion trying to make this more
visible.

Reported-By: Miles Delahunty
Author: Andres Freund
Discussion: https://postgr.es/m/CAOFAq3BU5Mf2TTvu8D9n_ZOoFAeQswuzk7yziAb7xuw_qyw5gw@mail.gmail.com
Backpatch: 10-
2022-02-21 08:57:34 -08:00
config Ensure the right perl is used for TAP tests on msys 2022-02-20 11:51:44 -05:00
contrib pgcrypto: Remove unused error code 2022-02-21 10:55:03 +01:00
doc doc: Mention environment variable ZSTD in the TAP tests for MSVC 2022-02-21 09:55:55 +09:00
src Fix temporary object cleanup failing due to toast access without snapshot. 2022-02-21 08:57:34 -08:00
.cirrus.yml ci: fix copy-paste mistake in 16eb8231d1. 2022-02-12 19:38:06 -08:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add another old commit to git-blame-ignore-revs. 2021-11-03 17:34:19 -07:00
.gitattributes gitattributes: Add new entry to silence whitespace error 2021-06-05 07:57:31 +02:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Ensure the right perl is used for TAP tests on msys 2022-02-20 11:51:44 -05:00
configure.ac Ensure the right perl is used for TAP tests on msys 2022-02-20 11:51:44 -05:00
COPYRIGHT Update copyright for 2022 2022-01-07 19:04:57 -05:00
GNUmakefile.in add missing tag from commit b8c4261e5e 2021-07-01 15:47:46 -04:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Dynamically find correct installation docs in Makefile. 2022-01-19 14:48:25 +01:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00

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
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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/.