From: Alexander Korotkov <akorotkov@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix tuple_fraction calculation in generate_orderedappend_paths()
Date: Sun, 18 May 2025 20:51:10 +0000
Message-ID: <E1uGkyT-002I7v-2b@gemulon.postgresql.org> (raw)
Fix tuple_fraction calculation in generate_orderedappend_paths()
6b94e7a6da adjusted generate_orderedappend_paths() to consider fractional
paths. However, it didn't manage to interpret the tuple_fraction value
correctly. According to the header comment of grouping_planner(), the
tuple_fraction >= 1 specifies the absolute number of expected tuples. That
number must be divided by the expected total number of tuples to get the
actual fraction.
Even though this is a bug fix, we don't backpatch it. The risks of the side
effects of plan changes on stable branches are too high.
Reported-by: Andrei Lepikhov <lepihov@gmail.com>
Discussion: https://postgr.es/m/3ca271fa-ca5c-458c-8934-eb148622b270%40gmail.com
Author: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/3d3a81fc24b07f04df81d898f6b4e85c553ef604
Modified Files
--------------
src/backend/optimizer/path/allpaths.c | 12 +++++++++++-
src/test/regress/expected/partition_join.out | 18 ++++++++++++++++++
src/test/regress/sql/partition_join.sql | 3 +++
3 files changed, 32 insertions(+), 1 deletion(-)
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To: pgsql-committers@postgresql.org
Cc: akorotkov@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix tuple_fraction calculation in generate_orderedappend_paths()
In-Reply-To: <E1uGkyT-002I7v-2b@gemulon.postgresql.org>
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