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help / color / mirror / Atom feedFrom: Amit Langote <amitlan@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Re-index ModifyTable FDW arrays when pruning result relations
Date: Tue, 23 Jun 2026 23:59:57 +0000
Message-ID: <E1wcB25-001b3f-1B@gemulon.postgresql.org> (raw)
Re-index ModifyTable FDW arrays when pruning result relations
ExecInitModifyTable() rebuilds the per-result-relation lists after
dropping result relations removed by initial runtime pruning. The
re-indexing was done for withCheckOptionLists, returningLists,
updateColnosLists, mergeActionLists and mergeJoinConditions, but
fdwPrivLists and fdwDirectModifyPlans were missed. As a result, a
kept foreign result relation could be handed the wrong fdw_private,
or ri_usesFdwDirectModify could be set from the wrong plan index,
leading to wrong behavior or a crash in BeginForeignModify() and in
the direct-modify path.
show_modifytable_info() had the same problem: it indexed the
plan-ordered node->fdwPrivLists with the post-pruning executor
position, so once initial pruning removed a result relation it
could read a different relation's fdw_private (often a NIL entry),
producing wrong EXPLAIN output or a crash.
Fix by re-indexing fdwPrivLists and fdwDirectModifyPlans alongside
the other lists, saving the re-indexed private lists in
ModifyTableState.mt_fdwPrivLists and reading from there in both
nodeModifyTable.c and explain.c.
Reported-by: Chi Zhang <798604270@qq.com>
Author: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Author: Rafia Sabih <rafia.pghackers@gmail.com>
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Etsuro Fujita <etsuro.fujita@gmail.com>
Discussion: https://postgr.es/m/19484-a3cb82c8cde3c8fa%40postgresql.org
Backpatch-through: 18
Branch
------
REL_18_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/1ef917e3a61a26a264fe65012d951ac36aa03732
Modified Files
--------------
contrib/postgres_fdw/expected/postgres_fdw.out | 64 ++++++++++++++++++++++++++
contrib/postgres_fdw/sql/postgres_fdw.sql | 34 ++++++++++++++
src/backend/commands/explain.c | 2 +-
src/backend/executor/nodeModifyTable.c | 22 ++++++++-
src/include/nodes/execnodes.h | 8 ++--
5 files changed, 124 insertions(+), 6 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: amitlan@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Re-index ModifyTable FDW arrays when pruning result relations
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