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Tom Lane f5de090cc1 Fix a recently-introduced race condition in LISTEN/NOTIFY handling. Commit `566372b3d` fixed some race conditions involving concurrent SimpleLruTruncate calls, but it introduced new ones in async.c. A newly-listening backend could attempt to read Notify SLRU pages that were in process of being truncated, possibly causing an error. Also, the QUEUE_TAIL pointer could become set to a value that's not equal to the queue position of any backend. While that's fairly harmless in v13 and up (thanks to commit `51004c717`), in older branches it resulted in near-permanent disabling of the queue truncation logic, so that continued use of NOTIFY led to queue-fill warnings and eventual inability to send any more notifies. (A server restart is enough to make that go away, but it's still pretty unpleasant.) The core of the problem is confusion about whether QUEUE_TAIL represents the "logical" tail of the queue (i.e., the oldest still-interesting data) or the "physical" tail (the oldest data we've not yet truncated away). To fix, split that into two variables. QUEUE_TAIL regains its definition as the logical tail, and we introduce a new variable to track the oldest un-truncated page. Per report from Mikael Gustavsson. Like the previous patch, back-patch to all supported branches. Discussion: https://postgr.es/m/1b8561412e8a4f038d7a491c8b922788@smhi.se		2020-11-28 14:03:40 -05:00
config	Update config.guess and config.sub	2020-04-30 09:06:49 +02:00
contrib	pg_trgm: fix crash in 2-item picksplit	2020-11-12 14:59:06 +00:00
doc	doc: Fix typos	2020-11-25 09:51:00 +01:00
src	Fix a recently-introduced race condition in LISTEN/NOTIFY handling.	2020-11-28 14:03:40 -05:00
.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	Fix configure's AC_CHECK_DECLS tests to work correctly with clang.	2018-11-19 12:01:47 -05:00
configure	On macOS, use -isysroot in link steps as well as compile steps.	2020-11-20 00:58:26 -05:00
configure.in	On macOS, use -isysroot in link steps as well as compile steps.	2020-11-20 00:58:26 -05:00
COPYRIGHT	Update copyrights for 2020	2020-01-01 12:21:45 -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

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/.