From c196c610b3391209ad43db22905ef5725dad559c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
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 <splarv@ya.ru>
Author: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
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 d1fbb6edc8a..50f158a54a4 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -8086,10 +8086,12 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan)
/*
* Ordinarily, the plan node should be a simple Result. However, if
* force_parallel_mode 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 (;;)
@@ -8107,7 +8109,7 @@ 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 $$
+declare
+ p_CurData refcursor;
+ val int;
+begin
+ open p_CurData scroll for select 42;
+ fetch p_CurData into val;
+ raise notice 'val = %', val;
+end; $$;
--
2.39.5