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a54e1f1587
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Andres Freund a54e1f1587 Fix bugs in vacuum of shared rels, by keeping their relcache entries current. 
When vacuum processes a relation it uses the corresponding relcache
entry's relfrozenxid / relminmxid as a cutoff for when to remove
tuples etc. Unfortunately for nailed relations (i.e. critical system
catalogs) bugs could frequently lead to the corresponding relcache
entry being stale.

This set of bugs could cause actual data corruption as vacuum would
potentially not remove the correct row versions, potentially reviving
them at a later point.  After 699bf7d05c some corruptions in this vein
were prevented, but the additional error checks could also trigger
spuriously. Examples of such errors are:
  ERROR: found xmin ... from before relfrozenxid ...
and
  ERROR: found multixact ... from before relminmxid ...
To be caused by this bug the errors have to occur on system catalog
tables.

The two bugs are:

1) Invalidations for nailed relations were ignored, based on the
   theory that the relcache entry for such tables doesn't
   change. Which is largely true, except for fields like relfrozenxid
   etc.  This means that changes to relations vacuumed in other
   sessions weren't picked up by already existing sessions.  Luckily
   autovacuum doesn't have particularly longrunning sessions.

2) For shared *and* nailed relations, the shared relcache init file
   was never invalidated while running.  That means that for such
   tables (e.g. pg_authid, pg_database) it's not just already existing
   sessions that are affected, but even new connections are as well.
   That explains why the reports usually were about pg_authid et. al.

To fix 1), revalidate the rd_rel portion of a relcache entry when
invalid. This implies a bit of extra complexity to deal with
bootstrapping, but it's not too bad.  The fix for 2) is simpler,
simply always remove both the shared and local init files.

Author: Andres Freund
Reviewed-By: Alvaro Herrera
Discussion:
    https://postgr.es/m/20180525203736.crkbg36muzxrjj5e@alap3.anarazel.de
    https://postgr.es/m/CAMa1XUhKSJd98JW4o9StWPrfS=11bPgG+_GDMxe25TvUY4Sugg@mail.gmail.com
    https://postgr.es/m/CAKMFJucqbuoDRfxPDX39WhA3vJyxweRg_zDVXzncr6+5wOguWA@mail.gmail.com
    https://postgr.es/m/CAGewt-ujGpMLQ09gXcUFMZaZsGJC98VXHEFbF-tpPB0fB13K+A@mail.gmail.com
Backpatch: 9.3-
2018-06-12 11:13:21 -07:00
config Update config.guess and config.sub 2018-06-11 08:54:58 -04:00
contrib Don't fall off the end of perl functions 2018-05-27 09:08:42 -04:00
doc doc: Replace non-ASCII lines in psql example output 2018-06-12 08:19:52 -04:00
src Fix bugs in vacuum of shared rels, by keeping their relcache entries current. 2018-06-12 11:13:21 -07:00
.dir-locals.el Make Emacs settings match perltidy configuration 2018-04-23 11:44:31 -04:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Add configure infrastructure (--with-llvm) to enable LLVM support. 2018-03-20 17:26:25 -07:00
configure Remove configure's check for nonstandard "long long" printf modifiers. 2018-05-23 14:19:04 -04:00
configure.in Remove configure's check for nonstandard "long long" printf modifiers. 2018-05-23 14:19:04 -04:00
COPYRIGHT Update copyright for 2018 2018-01-02 23:30:12 -05:00
GNUmakefile.in Have "make coverage" recurse into contrib as well 2016-09-05 18:44:36 -03:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:22 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00

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/.