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pg_dump: Fix performance regression in attribute statistics query.

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After adding pg_stats.tableid, we taught pg_dump to use it in the
attribute statistics query for servers running v19 or later.
Notably, we did not give this new form of the query a "redundant
filter clause" like we did the pre-v19 form.  Testing indicates
that produces a significant performance regression, and that adding
a similar filter clause to the v19-or-later form of the query fixes
it.

Oversight in commit 4b5ba0c4ca.

Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/apQ9nvLW_zFdarYd%40nathan
Backpatch-through: 19
This commit is contained in:
Nathan Bossart
2026-09-01 16:27:18 -05:00
parent 1bda0b23bc
commit 7da24355a2
1 changed files with 4 additions and 6 deletions
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10
src/bin/pg_dump/pg_dump.c
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@@ -11342,12 +11342,9 @@ dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
/*
* The results must be in the order of the relations supplied in the
* parameters to ensure we remain in sync as we walk through the TOC.
*
* For v9.4 through v18, the redundant filter clause on s.tablename =
* ANY(...) seems sufficient to convince the planner to use
* pg_class_relname_nsp_index, which avoids a full scan of pg_stats.
* In newer versions, pg_stats returns the table OIDs, eliminating the
* need for that hack.
* The redundant filter clause seems sufficient to convince the
* planner to use pg_class_relname_nsp_index, which avoids a full scan
* of pg_stats. This may not work for all versions.
*
* Our query for retrieving statistics for multiple relations uses
* WITH ORDINALITY and multi-argument UNNEST(), both of which were
@@ -11359,6 +11356,7 @@ dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
"FROM pg_catalog.pg_stats s "
"JOIN unnest($1) WITH ORDINALITY AS u (tableid, ord) "
"ON s.tableid = u.tableid "
"WHERE s.tableid = ANY($1) "
"ORDER BY u.ord, s.attname, s.inherited");
else if (fout->remoteVersion >= 90400)
appendPQExpBufferStr(query,