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Tom Lane 6e639267a5 YA attempt at taming worst-case behavior of get_actual_variable_range. 
We've made multiple attempts at preventing get_actual_variable_range
from taking an unreasonable amount of time (3ca930fc3, fccebe421).
But there's still an issue for the very first planning attempt after
deletion of a large number of extremal-valued tuples.  While that
planning attempt will set "killed" bits on the tuples it visits and
thereby reduce effort for next time, there's still a lot of work it
has to do to visit the heap and then set those bits.  It's (usually?)
not worth it to do that much work at plan time to have a slightly
better estimate, especially in a context like this where the table
contents are known to be mutating rapidly.

Therefore, let's bound the amount of work to be done by giving up
after we've visited 100 heap pages.  Giving up just means we'll
fall back on the extremal value recorded in pg_statistic, so it
shouldn't mean that planner estimates suddenly become worthless.

Note that this means we'll still gradually whittle down the problem
by setting a few more index "killed" bits in each planning attempt;
so eventually we'll reach a good state (barring further deletions),
even in the absence of VACUUM.

Simon Riggs, per a complaint from Jakub Wartak (with cosmetic
adjustments by me).  Back-patch to all supported branches.

Discussion: https://postgr.es/m/CAKZiRmznOwi0oaV=4PHOCM4ygcH4MgSvt8=5cu_vNCfc8FSUug@mail.gmail.com
 		2022-11-22 14:40:45 -05:00
config Suppress warning about stack_base_ptr with late-model GCC. 2022-02-17 22:45:34 -05:00
contrib Replace RelationOpenSmgr() with RelationGetSmgr(). 2022-11-17 16:54:30 -05:00
doc Replace link to Hunspell with the current homepage 2022-11-21 23:25:48 +01:00
src YA attempt at taming worst-case behavior of get_actual_variable_range. 2022-11-22 14:40:45 -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
.git-blame-ignore-revs Backpatch addition of .git-blame-ignore-revs 2022-08-05 19:36:24 +02:00
.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
COPYRIGHT Update copyright for 2022 2022-01-07 19:04:56 -05:00
GNUmakefile.in add missing tag from commit b8c4261e5e 2021-07-01 15:40:42 -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
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Stamp 13.9. 2022-11-07 16:45:38 -05:00
configure.in Stamp 13.9. 2022-11-07 16:45:38 -05:00

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/.