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Noah Misch 7da83415e5 Revive "snapshot too old" with wal_level=minimal and SET TABLESPACE.
Given a permanent relation rewritten in the current transaction, the
old_snapshot_threshold mechanism assumed the relation had never been
subject to early pruning.  Hence, a query could fail to report "snapshot
too old" when the rewrite followed an early truncation.  ALTER TABLE SET
TABLESPACE is probably the only rewrite mechanism capable of exposing
this bug.  REINDEX sets indcheckxmin, avoiding the problem.  CLUSTER has
zeroed page LSNs since before old_snapshot_threshold existed, so
old_snapshot_threshold has never cooperated with it.  ALTER TABLE
... SET DATA TYPE makes the table look empty to every past snapshot,
which is strictly worse.  Back-patch to v13, where commit
c6b92041d3 broke this.

Kyotaro Horiguchi and Noah Misch

Discussion: https://postgr.es/m/20210113.160705.2225256954956139776.horikyota.ntt@gmail.com
2021-01-30 00:12:18 -08:00
config Update copyright for 2021 2021-01-02 13:06:25 -05:00
contrib postgres_fdw: Fix tests for CLOBBER_CACHE_ALWAYS. 2021-01-30 10:12:22 +09:00
doc Doc: improve cross-references for SET/SHOW. 2021-01-29 10:46:14 -05:00
src Revive "snapshot too old" with wal_level=minimal and SET TABLESPACE. 2021-01-30 00:12:18 -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
.gitattributes gitattributes: Add new file 2019-11-12 08:13:55 +01:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Remove configure-time probe for DocBook DTD. 2020-11-30 15:24:13 -05:00
configure Introduce SHA1 implementations in the cryptohash infrastructure 2021-01-23 11:33:04 +09:00
configure.ac Introduce SHA1 implementations in the cryptohash infrastructure 2021-01-23 11:33:04 +09:00
COPYRIGHT Update copyright for 2021 2021-01-02 13:06:25 -05:00
GNUmakefile.in Make install-tests target work with vpath builds 2020-05-31 18:33:00 -04:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
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
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/.