From f120b614e070aed39586d1443193738a149a90d4 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 24 Mar 2017 12:30:39 -0400
Subject: [PATCH] plpgsql: Don't generate parallel plans for RETURN QUERY.
Commit 7aea8e4f2daa4b39ca9d1309a0c4aadb0f7ed81b allowed a parallel
plan to be generated when for a RETURN QUERY or RETURN QUERY EXECUTE
statement in a PL/pgsql block, but that's a bad idea because plplgsql
asks the executor for 50 rows at a time. That means that we'll always
be running serially a plan that was intended for parallel execution,
which is not a good idea. Fix by not requesting a parallel plan from
the outset.
Per discussion, back-patch to 9.6. There is a slight risk that, due
to optimizer error, somebody could have a case where the parallel plan
executed serially is actually faster than the supposedly-best serial
plan, but the consensus seems to be that that's not sufficient
justification for leaving 9.6 unpatched.
Discussion: http://postgr.es/m/CA+TgmoZ_ZuH+auEeeWnmtorPsgc_SmP+XWbDsJ+cWvWBSjNwDQ@mail.gmail.com
Discussion: http://postgr.es/m/CA+TgmobXEhvHbJtWDuPZM9bVSLiTj-kShxQJ2uM5GPDze9fRYA@mail.gmail.com
---
src/pl/plpgsql/src/pl_exec.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 49a4e622ffd..8e836a81494 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3023,7 +3023,7 @@ exec_stmt_return_query(PLpgSQL_execstate *estate,
if (stmt->query != NULL)
{
/* static query */
- exec_run_select(estate, stmt->query, 0, &portal, true);
+ exec_run_select(estate, stmt->query, 0, &portal, false);
}
else
{
@@ -3031,7 +3031,7 @@ exec_stmt_return_query(PLpgSQL_execstate *estate,
Assert(stmt->dynquery != NULL);
portal = exec_dynquery_with_params(estate, stmt->dynquery,
stmt->params, NULL,
- CURSOR_OPT_PARALLEL_OK);
+ 0);
}
/* Use eval_mcontext for tuple conversion work */
--
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