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Re-index ModifyTable FDW arrays when pruning result relations

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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
This commit is contained in:
Amit Langote 2026-06-22 17:21:45 +09:00
parent d3ff08e66b
commit 1ef917e3a6
5 changed files with 124 additions and 6 deletions
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64
contrib/postgres_fdw/expected/postgres_fdw.out
View file

@ -7132,6 +7132,70 @@ RESET enable_material;
DROP FOREIGN TABLE remt2;
DROP TABLE loct1;
DROP TABLE loct2;
-- Test that direct modify and foreign modify work with runtime pruning of
-- result relations (bug #19484)
create table fdw_part_update (a int not null, b int) partition by list (a);
create table fdw_part_update_p1 partition of fdw_part_update for values in (1);
create table fdw_part_update_remote (a int not null, b int);
create foreign table fdw_part_update_p2 partition of fdw_part_update
for values in (2)
server loopback options (table_name 'fdw_part_update_remote');
insert into fdw_part_update_p1 values (1, 10);
insert into fdw_part_update_remote values (2, 20);
set plan_cache_mode = force_generic_plan;
-- Check DirectModify case
prepare fdw_part_upd(int) as
update fdw_part_update set b = b + 1 where a = $1
returning tableoid::regclass, a, b;
explain (verbose, costs off)
execute fdw_part_upd(2);
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------
Update on public.fdw_part_update
Output: (fdw_part_update_1.tableoid)::regclass, fdw_part_update_1.a, fdw_part_update_1.b
Foreign Update on public.fdw_part_update_p2 fdw_part_update_2
-> Append
Subplans Removed: 1
-> Foreign Update on public.fdw_part_update_p2 fdw_part_update_2
Remote SQL: UPDATE public.fdw_part_update_remote SET b = (b + 1) WHERE ((a = $1::integer)) RETURNING a, b
(7 rows)
execute fdw_part_upd(2);
tableoid | a | b
--------------------+---+----
fdw_part_update_p2 | 2 | 21
(1 row)
deallocate fdw_part_upd;
-- Check ForeignModify case
prepare fdw_part_upd2(int) as
update fdw_part_update set b = b + random()::int * 0 + 1 where a = $1
returning tableoid::regclass, a, b;
explain (verbose, costs off)
execute fdw_part_upd2(2);
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------
Update on public.fdw_part_update
Output: (fdw_part_update_1.tableoid)::regclass, fdw_part_update_1.a, fdw_part_update_1.b
Foreign Update on public.fdw_part_update_p2 fdw_part_update_2
Remote SQL: UPDATE public.fdw_part_update_remote SET b = $2 WHERE ctid = $1 RETURNING a, b
-> Append
Subplans Removed: 1
-> Foreign Scan on public.fdw_part_update_p2 fdw_part_update_2
Output: ((fdw_part_update_2.b + ((random())::integer * 0)) + 1), fdw_part_update_2.tableoid, fdw_part_update_2.ctid, fdw_part_update_2.*
Remote SQL: SELECT a, b, ctid FROM public.fdw_part_update_remote WHERE ((a = $1::integer)) FOR UPDATE
(9 rows)
execute fdw_part_upd2(2);
tableoid | a | b
--------------------+---+----
fdw_part_update_p2 | 2 | 22
(1 row)
deallocate fdw_part_upd2;
reset plan_cache_mode;
drop table fdw_part_update;
drop table fdw_part_update_remote;
-- ===================================================================
-- test check constraints
-- ===================================================================

34
contrib/postgres_fdw/sql/postgres_fdw.sql
View file

@ -1732,6 +1732,40 @@ DROP FOREIGN TABLE remt2;
DROP TABLE loct1;
DROP TABLE loct2;
-- Test that direct modify and foreign modify work with runtime pruning of
-- result relations (bug #19484)
create table fdw_part_update (a int not null, b int) partition by list (a);
create table fdw_part_update_p1 partition of fdw_part_update for values in (1);
create table fdw_part_update_remote (a int not null, b int);
create foreign table fdw_part_update_p2 partition of fdw_part_update
for values in (2)
server loopback options (table_name 'fdw_part_update_remote');
insert into fdw_part_update_p1 values (1, 10);
insert into fdw_part_update_remote values (2, 20);
set plan_cache_mode = force_generic_plan;
-- Check DirectModify case
prepare fdw_part_upd(int) as
update fdw_part_update set b = b + 1 where a = $1
returning tableoid::regclass, a, b;
explain (verbose, costs off)
execute fdw_part_upd(2);
execute fdw_part_upd(2);
deallocate fdw_part_upd;
-- Check ForeignModify case
prepare fdw_part_upd2(int) as
update fdw_part_update set b = b + random()::int * 0 + 1 where a = $1
returning tableoid::regclass, a, b;
explain (verbose, costs off)
execute fdw_part_upd2(2);
execute fdw_part_upd2(2);
deallocate fdw_part_upd2;
reset plan_cache_mode;
drop table fdw_part_update;
drop table fdw_part_update_remote;
-- ===================================================================
-- test check constraints
-- ===================================================================

2
src/backend/commands/explain.c
View file

@ -4609,7 +4609,7 @@ show_modifytable_info(ModifyTableState *mtstate, List *ancestors,
fdwroutine != NULL &&
fdwroutine->ExplainForeignModify != NULL)
{
List *fdw_private = (List *) list_nth(node->fdwPrivLists, j);
List *fdw_private = (List *) list_nth(mtstate->mt_fdwPrivLists, j);
fdwroutine->ExplainForeignModify(mtstate,
resultRelInfo,

22
src/backend/executor/nodeModifyTable.c
View file

@ -4647,6 +4647,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
List *updateColnosLists = NIL;
List *mergeActionLists = NIL;
List *mergeJoinConditions = NIL;
List *fdwPrivLists = NIL;
Bitmapset *fdwDirectModifyPlans = NULL;
ResultRelInfo *resultRelInfo;
List *arowmarks;
ListCell *l;
@ -4689,6 +4691,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
if (keep_rel)
{
List *fdwPrivList = (List *) list_nth(node->fdwPrivLists, i);
resultRelations = lappend_int(resultRelations, rti);
if (node->withCheckOptionLists)
{
@ -4724,6 +4728,19 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
mergeJoinConditions = lappend(mergeJoinConditions, mergeJoinCondition);
}
/*
* fdwPrivLists/fdwDirectModifyPlans are re-indexed to match
* resultRelations
*/
fdwPrivLists = lappend(fdwPrivLists, fdwPrivList);
if (bms_is_member(i, node->fdwDirectModifyPlans))
{
int new_index = list_length(resultRelations) - 1;
fdwDirectModifyPlans = bms_add_member(fdwDirectModifyPlans,
new_index);
}
}
i++;
}
@ -4753,6 +4770,7 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
mtstate->mt_updateColnosLists = updateColnosLists;
mtstate->mt_mergeActionLists = mergeActionLists;
mtstate->mt_mergeJoinConditions = mergeJoinConditions;
mtstate->mt_fdwPrivLists = fdwPrivLists;
/*----------
* Resolve the target relation. This is the same as:
@ -4828,7 +4846,7 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
/* Initialize the usesFdwDirectModify flag */
resultRelInfo->ri_usesFdwDirectModify =
bms_is_member(i, node->fdwDirectModifyPlans);
bms_is_member(i, fdwDirectModifyPlans);
/*
* Verify result relation is a valid target for the current operation
@ -4857,7 +4875,7 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
resultRelInfo->ri_FdwRoutine != NULL &&
resultRelInfo->ri_FdwRoutine->BeginForeignModify != NULL)
{
List *fdw_private = (List *) list_nth(node->fdwPrivLists, i);
List *fdw_private = (List *) list_nth(fdwPrivLists, i);
resultRelInfo->ri_FdwRoutine->BeginForeignModify(mtstate,
resultRelInfo,

8
src/include/nodes/execnodes.h
View file

@ -1453,13 +1453,15 @@ typedef struct ModifyTableState
double mt_merge_deleted;
/*
* Lists of valid updateColnosLists, mergeActionLists, and
* mergeJoinConditions. These contain only entries for unpruned
* relations, filtered from the corresponding lists in ModifyTable.
* Lists of valid updateColnosLists, mergeActionLists,
* mergeJoinConditions, and fdwPrivLists. These contain only entries for
* unpruned relations, filtered from the corresponding lists in
* ModifyTable.
*/
List *mt_updateColnosLists;
List *mt_mergeActionLists;
List *mt_mergeJoinConditions;
List *mt_fdwPrivLists;
} ModifyTableState;
/* ----------------