From: Alexander Korotkov <akorotkov@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Improve statistics estimation for single-column GROUP BY in sub-
Date: Wed, 19 Feb 2025 09:59:48 +0000
Message-ID: <E1tkgrt-0006xK-0o@gemulon.postgresql.org> (raw)
Improve statistics estimation for single-column GROUP BY in sub-queries
This commit follows the idea of the 4767bc8ff2. If sub-query has only one
GROUP BY column, we can consider its output variable as being unique. We can
employ this fact in the statistics to make more precise estimations in the
upper query block.
Author: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/e983ee9380fcac746f9b6b7c360d255d9fcd0907
Modified Files
--------------
src/backend/utils/adt/selfuncs.c | 53 +++++++++++++++++++--------------
src/include/utils/selfuncs.h | 3 +-
src/test/regress/expected/stats_ext.out | 15 ++++++++++
src/test/regress/sql/stats_ext.sql | 12 ++++++++
4 files changed, 60 insertions(+), 23 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: akorotkov@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Improve statistics estimation for single-column GROUP BY in sub-
In-Reply-To: <E1tkgrt-0006xK-0o@gemulon.postgresql.org>
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