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Fix plpgsql's handling of simple expressions in scrollable cursors.

author Tom Lane <tgl@sss.pgh.pa.us>

2025年3月21日 15:30:42 +0000 (11:30 -0400)

committer Tom Lane <tgl@sss.pgh.pa.us>

2025年3月21日 15:30:42 +0000 (11:30 -0400)

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 patch | blob | blame | history

src/pl/plpgsql/src/pl_exec.c patch | blob | blame | history

src/pl/plpgsql/src/sql/plpgsql_simple.sql patch | blob | blame | history

diff --git a/src/pl/plpgsql/src/expected/plpgsql_simple.out b/src/pl/plpgsql/src/expected/plpgsql_simple.out

index 7b22e60f1984ff07c526673212510c94cb58ee46..da351873e742e56dfc455d86541235f378d83588 100644 (file)

--- 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 ac87e6b83bb01231b5899eae91d21dfb9d0244e7..6469807a078c5bae959430dd346d6c9ba027dee8 100644 (file)

--- a/src/pl/plpgsql/src/pl_exec.c

+++ b/src/pl/plpgsql/src/pl_exec.c

@@ -8136,10 +8136,12 @@ 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 (;;)

@@ -8157,7 +8159,7 @@ 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 143bf09dce4694e2ce003f9b0aa9b89f6ca38db4..72d8afe4500d13ee13acac4f1b82601bb1032e55 100644 (file)

--- 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; $$;

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