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help / color / mirror / Atom feedFrom: Peter Eisentraut <peter@eisentraut.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Don't evaluate the FOR PORTION OF target under EXPLAIN
Date: Tue, 08 Sep 2026 13:31:26 +0000
Message-ID: <E1x3vv3-00000003zyW-03Fn@gemulon.postgresql.org> (raw)
Don't evaluate the FOR PORTION OF target under EXPLAIN
ExecInitModifyTable() evaluated ForPortionOfExpr.targetRange
unconditionally at executor start-up, with no EXEC_FLAG_EXPLAIN_ONLY
guard. This caused three problems:
- EXPLAIN (GENERIC_PLAN) failed with "no value found for parameter 1".
- Plain EXPLAIN with FOR PORTION OF (null) raised "FOR PORTION OF
target must not be null".
- Plain EXPLAIN ran user functions appearing in the target a second
time, beyond the one evaluation the planner already does for
selectivity estimation.
Now we skip the evaluation and the accompanying null check in
explain-only mode.
Reported-by: Noah Misch <noah@leadboat.com>
Author: Paul A. Jungwirth <pj@illuminatedcomputing.com>
Discussion: https://www.postgresql.org/message-id/flat/CA%2BrenyXci9khYXJ8uSwzF30DVw%2Bzc4QwGb1RdsuOu_YtrFuy1g%4...
Branch
------
REL_19_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/98f6984e5c0d180264d1e972c36252c8b36206ef
Modified Files
--------------
src/backend/executor/nodeModifyTable.c | 40 +++++++------
src/test/regress/expected/for_portion_of.out | 89 ++++++++++++++++++++++++++++
src/test/regress/sql/for_portion_of.sql | 44 ++++++++++++++
3 files changed, 156 insertions(+), 17 deletions(-)
view thread (2+ messages)
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To: pgsql-committers@postgresql.org
Cc: peter@eisentraut.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Don't evaluate the FOR PORTION OF target under EXPLAIN
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