From: Alexander Korotkov <akorotkov@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix usage of the parse tree for estimate_num_groups() in set ope
Date: Sat, 04 Nov 2023 01:30:29 +0000
Message-ID: <E1qz5Ub-003pkj-CP@gemulon.postgresql.org> (raw)
Fix usage of the parse tree for estimate_num_groups() in set operations
recurse_set_operations() uses the parse tree for the group number estimation,
because of the "varno 0" hack. At the same time 2489d76c49 made root->parse
and corresponding parent_root->simple_rte_array[]->subquery distinct copies
of the parse tree, while d3d55ce571 introduced self-join removal replacing
relid of removed relation only in one of the copies.
The present commit fixes this bug by making recurse_set_operations() call
estimate_num_groups() with the copy of the parse tree processed by self-join
removal.
In future, we may think about maintaining just one copy of the parse tree
and/or keeping removed relids as aliases.
Reported-by: Zuming Jiang
Bug: #18170
Discussion: https://postgr.es/m/flat/18170-f1d17bf9a0d58b24%40postgresql.org
Author: Richard Guo, Alexander Korotkov
Reviewed-by: Andrei Lepikhov
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/ec63622c03ff7be36d32c08aaa7d853856451488
Modified Files
--------------
src/backend/optimizer/prep/prepunion.c | 7 +++++--
src/test/regress/expected/join.out | 17 +++++++++++++++++
src/test/regress/sql/join.sql | 7 +++++++
3 files changed, 29 insertions(+), 2 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: akorotkov@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix usage of the parse tree for estimate_num_groups() in set ope
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