postgres/contrib/pgstattuple
Michael Paquier 684a745f55 pgstattuple: Improve reports generated for indexes (hash, gist, btree)
pgstattuple checks the state of the pages retrieved for gist and hash
using some check functions from each index AM, respectively
gistcheckpage() and _hash_checkpage().  When these are called, they
would fail when bumping on data that is found as incorrect (like opaque
area size not matching, or empty pages), contrary to btree that simply
discards these cases and continues to aggregate data.

Zero pages can happen after a crash, with these AMs being able to do an
internal cleanup when these are seen.  Also, sporadic failures are
annoying when doing for example a large-scale diagnostic query based on
pgstattuple with a join of pg_class, as it forces one to use tricks like
quals to discard hash or gist indexes, or use a PL wrapper able to catch
errors.

This commit changes the reports generated for btree, gist and hash to
be more user-friendly;
- When seeing an empty page, report it as free space.  This new rule
applies to gist and hash, and already applied to btree.
- For btree, a check based on the size of BTPageOpaqueData is added.
- For gist indexes, gistcheckpage() is not called anymore, replaced by a
check based on the size of GISTPageOpaqueData.
- For hash indexes, instead of _hash_getbuf_with_strategy(), use a
direct call to ReadBufferExtended(), coupled with a check based on
HashPageOpaqueData.  The opaque area size check was already used.
- Pages that do not match these criterias are discarded from the stats
reports generated.

There have been a couple of bug reports over the years that complained
about the current behavior for hash and gist, as being not that useful,
with nothing being done about it.  Hence this change is backpatched down
to v13.

Reported-by: Noah Misch <noah@leadboat.com>
Author: Nitin Motiani <nitinmotiani@google.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/CAH5HC95gT1J3dRYK4qEnaywG8RqjbwDdt04wuj8p39R=HukayA@mail.gmail.com
Backpatch-through: 13
2025-10-02 11:07:30 +09:00
..
expected Reintroduce support for sequences in pgstattuple and pageinspect. 2024-09-12 16:31:29 -05:00
sql Reintroduce support for sequences in pgstattuple and pageinspect. 2024-09-12 16:31:29 -05:00
.gitignore Add a regression test for pgstattuple. 2011-08-25 00:06:16 -04:00
Makefile Remove support for upgrading extensions from "unpackaged" state. 2020-02-19 16:59:14 -05:00
meson.build Update copyright for 2025 2025-01-01 11:21:55 -05:00
pgstatapprox.c Update copyright for 2025 2025-01-01 11:21:55 -05:00
pgstatindex.c Remove unneeded casts of BufferGetPage() result 2025-08-29 07:18:29 +02:00
pgstattuple--1.1--1.2.sql Fix pgstattuple functions to use regclass-type as the argument. 2013-07-19 03:50:20 +09:00
pgstattuple--1.2--1.3.sql Add pgstattuple_approx() to the pgstattuple extension. 2015-05-13 07:35:06 +02:00
pgstattuple--1.3--1.4.sql Update pgstattuple extension for parallel query. 2016-06-10 10:42:03 -04:00
pgstattuple--1.4--1.5.sql Fix pgstattuple's handling of unused hash pages. 2017-04-12 11:53:00 -04:00
pgstattuple--1.4.sql Minor fixes in contrib installation scripts. 2016-06-14 10:47:06 -04:00
pgstattuple--1.0--1.1.sql Add pgstatginindex() function to get the size of the GIN pending list. 2012-12-05 09:58:03 +02:00
pgstattuple.c pgstattuple: Improve reports generated for indexes (hash, gist, btree) 2025-10-02 11:07:30 +09:00
pgstattuple.control Remove superuser checks in pgstattuple 2016-09-29 22:13:38 -04:00