diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 12214f8a150..65e52cca630 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -503,7 +503,7 @@ init_execution_state(List *queryTree_list,
 			}
 			else
 				stmt = pg_plan_query(queryTree,
-						  fcache->readonly_func ? CURSOR_OPT_PARALLEL_OK : 0,
+									 CURSOR_OPT_PARALLEL_OK,
 									 NULL);
 
 			/*
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 72c7b4d0689..eeaa4805e4d 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -314,7 +314,7 @@ SPI_execute(const char *src, bool read_only, long tcount)
 
 	memset(&plan, 0, sizeof(_SPI_plan));
 	plan.magic = _SPI_PLAN_MAGIC;
-	plan.cursor_options = 0;
+	plan.cursor_options = CURSOR_OPT_PARALLEL_OK;
 
 	_SPI_prepare_oneshot_plan(src, &plan);
 
@@ -458,7 +458,7 @@ SPI_execute_with_args(const char *src,
 
 	memset(&plan, 0, sizeof(_SPI_plan));
 	plan.magic = _SPI_PLAN_MAGIC;
-	plan.cursor_options = 0;
+	plan.cursor_options = CURSOR_OPT_PARALLEL_OK;
 	plan.nargs = nargs;
 	plan.argtypes = argtypes;
 	plan.parserSetup = NULL;
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 8e836a81494..664fc425143 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -264,8 +264,7 @@ static Datum exec_eval_expr(PLpgSQL_execstate *estate,
 			   Oid *rettype,
 			   int32 *rettypmod);
 static int exec_run_select(PLpgSQL_execstate *estate,
-				PLpgSQL_expr *expr, long maxtuples, Portal *portalP,
-				bool parallelOK);
+				PLpgSQL_expr *expr, long maxtuples, Portal *portalP);
 static int exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
 			   Portal portal, bool prefetch_ok);
 static ParamListInfo setup_param_list(PLpgSQL_execstate *estate,
@@ -1685,7 +1684,7 @@ exec_stmt_perform(PLpgSQL_execstate *estate, PLpgSQL_stmt_perform *stmt)
 {
 	PLpgSQL_expr *expr = stmt->expr;
 
-	(void) exec_run_select(estate, expr, 0, NULL, true);
+	(void) exec_run_select(estate, expr, 0, NULL);
 	exec_set_found(estate, (estate->eval_processed != 0));
 	exec_eval_cleanup(estate);
 
@@ -2238,7 +2237,7 @@ exec_stmt_fors(PLpgSQL_execstate *estate, PLpgSQL_stmt_fors *stmt)
 	/*
 	 * Open the implicit cursor for the statement using exec_run_select
 	 */
-	exec_run_select(estate, stmt->query, 0, &portal, false);
+	exec_run_select(estate, stmt->query, 0, &portal);
 
 	/*
 	 * Execute the loop
@@ -3023,7 +3022,7 @@ exec_stmt_return_query(PLpgSQL_execstate *estate,
 	if (stmt->query != NULL)
 	{
 		/* static query */
-		exec_run_select(estate, stmt->query, 0, &portal, false);
+		exec_run_select(estate, stmt->query, 0, &portal);
 	}
 	else
 	{
@@ -3627,7 +3626,7 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
 	{
 		ListCell   *l;
 
-		exec_prepare_plan(estate, expr, 0);
+		exec_prepare_plan(estate, expr, CURSOR_OPT_PARALLEL_OK);
 		stmt->mod_stmt = false;
 		foreach(l, SPI_plan_get_plan_sources(expr->plan))
 		{
@@ -5174,7 +5173,7 @@ exec_eval_expr(PLpgSQL_execstate *estate,
 	 * If first time through, create a plan for this expression.
 	 */
 	if (expr->plan == NULL)
-		exec_prepare_plan(estate, expr, 0);
+		exec_prepare_plan(estate, expr, CURSOR_OPT_PARALLEL_OK);
 
 	/*
 	 * If this is a simple expression, bypass SPI and use the executor
@@ -5187,7 +5186,7 @@ exec_eval_expr(PLpgSQL_execstate *estate,
 	/*
 	 * Else do it the hard way via exec_run_select
 	 */
-	rc = exec_run_select(estate, expr, 2, NULL, false);
+	rc = exec_run_select(estate, expr, 2, NULL);
 	if (rc != SPI_OK_SELECT)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -5243,18 +5242,23 @@ exec_eval_expr(PLpgSQL_execstate *estate,
  */
 static int
 exec_run_select(PLpgSQL_execstate *estate,
-				PLpgSQL_expr *expr, long maxtuples, Portal *portalP,
-				bool parallelOK)
+				PLpgSQL_expr *expr, long maxtuples, Portal *portalP)
 {
 	ParamListInfo paramLI;
 	int			rc;
 
 	/*
-	 * On the first call for this expression generate the plan
+	 * On the first call for this expression generate the plan.
+	 *
+	 * If we don't need to return a portal, then we're just going to execute
+	 * the query once, which means it's OK to use a parallel plan, even if the
+	 * number of rows being fetched is limited.  If we do need to return a
+	 * portal, the caller might do cursor operations, which parallel query
+	 * can't support.
 	 */
 	if (expr->plan == NULL)
-		exec_prepare_plan(estate, expr, parallelOK ?
-						  CURSOR_OPT_PARALLEL_OK : 0);
+		exec_prepare_plan(estate, expr,
+						  portalP == NULL ? CURSOR_OPT_PARALLEL_OK : 0);
 
 	/*
 	 * If a portal was requested, put the query into the portal