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

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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
This commit is contained in:
Tom Lane
2025-03-21 11:30:42 -04:00
parent 40c9592712
commit 5e56efa7c0
3 changed files with 30 additions and 5 deletions
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11
src/pl/plpgsql/src/expected/plpgsql_simple.out
View File

@@ -118,3 +118,14 @@ select simplecaller();
44 44
(1 row) (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

12
src/pl/plpgsql/src/pl_exec.c
View File

@@ -8136,10 +8136,12 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan)
/* /*
* Ordinarily, the plan node should be a simple Result. However, if * Ordinarily, the plan node should be a simple Result. However, if
* force_parallel_mode is on, the planner might've stuck a Gather node * 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 * atop that; and/or if this plan is for a scrollable cursor, the planner
* Gather node. The Gather node's tlist would normally contain a Var * might've stuck a Material node atop it. The simplest way to deal with
* referencing the child node's output, but it could also be a Param, or * this is to look through the Gather and/or Material nodes. The upper
* it could be a Const that setrefs.c copied as-is. * 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; plan = stmt->planTree;
for (;;) for (;;)
@@ -8157,7 +8159,7 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan)
((Result *) plan)->resconstantqual == NULL); ((Result *) plan)->resconstantqual == NULL);
break; break;
} }
else if (IsA(plan, Gather)) else if (IsA(plan, Gather) || IsA(plan, Material))
{ {
Assert(plan->lefttree != NULL && Assert(plan->lefttree != NULL &&
plan->righttree == NULL && plan->righttree == NULL &&

12
src/pl/plpgsql/src/sql/plpgsql_simple.sql
View File

@@ -102,3 +102,15 @@ as $$select 22 + 22$$;
select simplecaller(); select simplecaller();
select simplecaller(); select simplecaller();
-- Check handling of simple expression in a scrollable cursor (bug #18859)
do $$
declare
p_CurData refcursor;
val int;
begin
open p_CurData scroll for select 42;
fetch p_CurData into val;
raise notice 'val = %', val;
end; $$;