From 1353b1161a790e64507428e33cc0c5975f26474b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 21 Mar 2025 11:30:42 -0400 Subject: [PATCH] Fix plpgsql's handling of simple expressions in scrollable cursors. exec_save_simple_expr did not account for the possibility that standard_planner would stick a Materialize node atop the plan of even a simple Result, if CURSOR_OPT_SCROLL is set. This led to an "unexpected plan node type" error. This is a very old bug, but it'd only be reached by declaring a cursor for a "SELECT simple-expression" query and explicitly marking it scrollable, which is an odd thing to do. So the lack of prior reports isn't too surprising. Bug: #18859 Reported-by: Olleg Samoylov Author: Andrei Lepikhov Reviewed-by: Tom Lane Discussion: https://postgr.es/m/18859-0d5f28ac99a37059@postgresql.org Backpatch-through: 13 --- src/pl/plpgsql/src/expected/plpgsql_simple.out | 11 +++++++++++ src/pl/plpgsql/src/pl_exec.c | 12 +++++++----- src/pl/plpgsql/src/sql/plpgsql_simple.sql | 12 ++++++++++++ 3 files changed, 30 insertions(+), 5 deletions(-) diff --git a/src/pl/plpgsql/src/expected/plpgsql_simple.out b/src/pl/plpgsql/src/expected/plpgsql_simple.out index 7b22e60f198..da351873e74 100644 --- a/src/pl/plpgsql/src/expected/plpgsql_simple.out +++ b/src/pl/plpgsql/src/expected/plpgsql_simple.out @@ -118,3 +118,14 @@ select simplecaller(); 44 (1 row) +-- Check handling of simple expression in a scrollable cursor (bug #18859) +do $$ +declare + p_CurData refcursor; + val int; +begin + open p_CurData scroll for select 42; + fetch p_CurData into val; + raise notice 'val = %', val; +end; $$; +NOTICE: val = 42 diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c index ea9740e3f89..ca3d1e753bc 100644 --- a/src/pl/plpgsql/src/pl_exec.c +++ b/src/pl/plpgsql/src/pl_exec.c @@ -8141,10 +8141,12 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan) /* * Ordinarily, the plan node should be a simple Result. However, if * debug_parallel_query is on, the planner might've stuck a Gather node - * atop that. The simplest way to deal with this is to look through the - * Gather node. The Gather node's tlist would normally contain a Var - * referencing the child node's output, but it could also be a Param, or - * it could be a Const that setrefs.c copied as-is. + * atop that; and/or if this plan is for a scrollable cursor, the planner + * might've stuck a Material node atop it. The simplest way to deal with + * this is to look through the Gather and/or Material nodes. The upper + * node's tlist would normally contain a Var referencing the child node's + * output, but it could also be a Param, or it could be a Const that + * setrefs.c copied as-is. */ plan = stmt->planTree; for (;;) @@ -8162,7 +8164,7 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan) ((Result *) plan)->resconstantqual == NULL); break; } - else if (IsA(plan, Gather)) + else if (IsA(plan, Gather) || IsA(plan, Material)) { Assert(plan->lefttree != NULL && plan->righttree == NULL && diff --git a/src/pl/plpgsql/src/sql/plpgsql_simple.sql b/src/pl/plpgsql/src/sql/plpgsql_simple.sql index 143bf09dce4..72d8afe4500 100644 --- a/src/pl/plpgsql/src/sql/plpgsql_simple.sql +++ b/src/pl/plpgsql/src/sql/plpgsql_simple.sql @@ -102,3 +102,15 @@ as $$select 22 + 22$$; select simplecaller(); select simplecaller(); + +-- Check handling of simple expression in a scrollable cursor (bug #18859) + +do $$ +declare + p_CurData refcursor; + val int; +begin + open p_CurData scroll for select 42; + fetch p_CurData into val; + raise notice 'val = %', val; +end; $$;