From a404885ad2f94b3216b656f0b21ad987713733b2 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 21 May 2025 12:00:38 -0400 Subject: [PATCH] In ExecInitModifyTable, don't scribble on the source plan. The code carelessly modified mtstate->ps.plan->targetlist, which it's not supposed to do. Fortunately, there's not really any need to do that because the planner already set up a perfectly acceptable targetlist for the plan node. We just need to remove the erroneous assignments and update some relevant comments. As it happens, the erroneous assignments caused the targetlist to point to a different part of the source plan tree, so that there isn't really a risk of the pointer becoming dangling after executor termination. The only visible effect we can find is that EXPLAIN will show upper references to the ModifyTable's output expressions using different variables. Formerly it showed Vars from the first target relation that survived executor-startup pruning. Now it always shows such references using the first relation appearing in the planner output, independently of what happens during executor pruning. On the whole that seems like a good thing. (We do need a small tweak in ExplainPreScanNode to ensure that that relation will receive a refname assignment in set_rtable_names, even if it got pruned at startup.) Reported-by: Tom Lane Author: Andres Freund Co-authored-by: Tom Lane Discussion: https://postgr.es/m/213261.1747611093@sss.pgh.pa.us --- src/backend/commands/explain.c | 4 ++ src/backend/executor/nodeModifyTable.c | 10 ++-- src/backend/optimizer/plan/setrefs.c | 7 +-- src/test/regress/expected/partition_prune.out | 47 ++++++++++--------- src/test/regress/sql/partition_prune.sql | 6 +-- 5 files changed, 41 insertions(+), 33 deletions(-) diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index 786ee865f147..45942b4dd4f0 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -1232,6 +1232,10 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used) if (((ModifyTable *) plan)->exclRelRTI) *rels_used = bms_add_member(*rels_used, ((ModifyTable *) plan)->exclRelRTI); + /* Ensure Vars used in RETURNING will have refnames */ + if (plan->targetlist) + *rels_used = bms_add_member(*rels_used, + linitial_int(((ModifyTable *) plan)->resultRelations)); break; case T_Append: *rels_used = bms_add_members(*rels_used, diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c index 46d533b72880..2bc89bf84dc3 100644 --- a/src/backend/executor/nodeModifyTable.c +++ b/src/backend/executor/nodeModifyTable.c @@ -4830,12 +4830,11 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags) ExprContext *econtext; /* - * Initialize result tuple slot and assign its rowtype using the first - * RETURNING list. We assume the rest will look the same. + * Initialize result tuple slot and assign its rowtype using the plan + * node's declared targetlist, which the planner set up to be the same + * as the first (before runtime pruning) RETURNING list. We assume + * all the result rels will produce compatible output. */ - mtstate->ps.plan->targetlist = (List *) linitial(returningLists); - - /* Set up a slot for the output of the RETURNING projection(s) */ ExecInitResultTupleSlotTL(&mtstate->ps, &TTSOpsVirtual); slot = mtstate->ps.ps_ResultTupleSlot; @@ -4865,7 +4864,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags) * We still must construct a dummy result tuple type, because InitPlan * expects one (maybe should change that?). */ - mtstate->ps.plan->targetlist = NIL; ExecInitResultTypeTL(&mtstate->ps); mtstate->ps.ps_ExprContext = NULL; diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c index 150e9f060ee0..8e1eb77dd494 100644 --- a/src/backend/optimizer/plan/setrefs.c +++ b/src/backend/optimizer/plan/setrefs.c @@ -1097,9 +1097,10 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset) /* * Set up the visible plan targetlist as being the same as - * the first RETURNING list. This is for the use of - * EXPLAIN; the executor won't pay any attention to the - * targetlist. We postpone this step until here so that + * the first RETURNING list. This is mostly for the use + * of EXPLAIN; the executor won't execute that targetlist, + * although it does use it to prepare the node's result + * tuple slot. We postpone this step until here so that * we don't have to do set_returning_clause_references() * twice on identical targetlists. */ diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out index 0bf35260b46e..d1966cd7d829 100644 --- a/src/test/regress/expected/partition_prune.out +++ b/src/test/regress/expected/partition_prune.out @@ -4553,16 +4553,18 @@ create view part_abc_view as select * from part_abc where b <> 'a' with check op prepare update_part_abc_view as update part_abc_view set b = $2 where a = $1 returning *; -- Only the unpruned partition should be shown in the list of relations to be -- updated -explain (costs off) execute update_part_abc_view (1, 'd'); - QUERY PLAN -------------------------------------------------------- - Update on part_abc - Update on part_abc_1 +explain (verbose, costs off) execute update_part_abc_view (1, 'd'); + QUERY PLAN +----------------------------------------------------------------------------- + Update on public.part_abc + Output: part_abc_1.a, part_abc_1.b, part_abc_1.c + Update on public.part_abc_1 -> Append Subplans Removed: 1 - -> Seq Scan on part_abc_1 - Filter: ((b <> 'a'::text) AND (a = $1)) -(6 rows) + -> Seq Scan on public.part_abc_1 + Output: $2, part_abc_1.tableoid, part_abc_1.ctid + Filter: ((part_abc_1.b <> 'a'::text) AND (part_abc_1.a = $1)) +(8 rows) execute update_part_abc_view (1, 'd'); a | b | c @@ -4570,28 +4572,31 @@ execute update_part_abc_view (1, 'd'); 1 | d | t (1 row) -explain (costs off) execute update_part_abc_view (2, 'a'); - QUERY PLAN -------------------------------------------------------- - Update on part_abc - Update on part_abc_2 part_abc_1 +explain (verbose, costs off) execute update_part_abc_view (2, 'a'); + QUERY PLAN +----------------------------------------------------------------------------- + Update on public.part_abc + Output: part_abc_1.a, part_abc_1.b, part_abc_1.c + Update on public.part_abc_2 -> Append Subplans Removed: 1 - -> Seq Scan on part_abc_2 part_abc_1 - Filter: ((b <> 'a'::text) AND (a = $1)) -(6 rows) + -> Seq Scan on public.part_abc_2 + Output: $2, part_abc_2.tableoid, part_abc_2.ctid + Filter: ((part_abc_2.b <> 'a'::text) AND (part_abc_2.a = $1)) +(8 rows) execute update_part_abc_view (2, 'a'); ERROR: new row violates check option for view "part_abc_view" DETAIL: Failing row contains (2, a, t). -- All pruned. -explain (costs off) execute update_part_abc_view (3, 'a'); - QUERY PLAN ------------------------------ - Update on part_abc +explain (verbose, costs off) execute update_part_abc_view (3, 'a'); + QUERY PLAN +---------------------------------------------------- + Update on public.part_abc + Output: part_abc_1.a, part_abc_1.b, part_abc_1.c -> Append Subplans Removed: 2 -(3 rows) +(4 rows) execute update_part_abc_view (3, 'a'); a | b | c diff --git a/src/test/regress/sql/partition_prune.sql b/src/test/regress/sql/partition_prune.sql index f6db9479f54a..d93c0c03baba 100644 --- a/src/test/regress/sql/partition_prune.sql +++ b/src/test/regress/sql/partition_prune.sql @@ -1371,12 +1371,12 @@ create view part_abc_view as select * from part_abc where b <> 'a' with check op prepare update_part_abc_view as update part_abc_view set b = $2 where a = $1 returning *; -- Only the unpruned partition should be shown in the list of relations to be -- updated -explain (costs off) execute update_part_abc_view (1, 'd'); +explain (verbose, costs off) execute update_part_abc_view (1, 'd'); execute update_part_abc_view (1, 'd'); -explain (costs off) execute update_part_abc_view (2, 'a'); +explain (verbose, costs off) execute update_part_abc_view (2, 'a'); execute update_part_abc_view (2, 'a'); -- All pruned. -explain (costs off) execute update_part_abc_view (3, 'a'); +explain (verbose, costs off) execute update_part_abc_view (3, 'a'); execute update_part_abc_view (3, 'a'); deallocate update_part_abc_view;