pl_parallel_v1.patch

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index a666391..fc5c82f 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1596,6 +1596,22 @@ ExecutePlan(EState *estate,
 		EnterParallelMode();
 
 	/*
+	 * For SQL or other PL functions, the supplied numberTuples is always
+	 * one, thus, upper condition restricts parallelism for the queries
+	 * coming from these functions. To enable such parallelism, we ignore the
+	 * numberTuples check and identify if the planner considers it safe to use
+	 * parallelism for this query and it is coming only from PL or SQL
+	 * functions.
+	 */
+
+	else if (estate->es_plannedstmt->parallelModeNeeded &&
+		(dest->mydest == DestSPI || dest->mydest == DestSQLFunction))
+	{
+		use_parallel_mode = true;
+		EnterParallelMode();
+	}
+
+	/*
 	 * Loop until we've processed the proper number of tuples from the plan.
 	 */
 	for (;;)
@@ -1660,7 +1676,16 @@ ExecutePlan(EState *estate,
 		 */
 		current_tuple_count++;
 		if (numberTuples && numberTuples == current_tuple_count)
+		{
+			/*
+			 * For the queries coming from SQL or PL functions, this condition
+			 * will be satisfied for the first tuple and since we enabled
+			 * parallel workers for it, a proper shutdown of the workers would
+			 * be required.
+			 */
+			(void) ExecShutdownNode(planstate);
 			break;
+		}
 	}
 
 	if (use_parallel_mode)
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 55f97b1..45114d2 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -314,7 +314,12 @@ 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;
+
+	/* Allow parallelism if the query is read-only */
+	if(read_only)
+		plan.cursor_options = CURSOR_OPT_PARALLEL_OK;
+	else
+		plan.cursor_options = 0;
 
 	_SPI_prepare_oneshot_plan(src, &plan);
 
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 6fc3db0..27c9e47 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3625,7 +3625,12 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
 	{
 		ListCell   *l;
 
-		exec_prepare_plan(estate, expr, 0);
+		/* Allow parallelism if the function is not trigger type. */
+		if (estate->func->fn_is_trigger == PLPGSQL_NOT_TRIGGER)
+			exec_prepare_plan(estate, expr, CURSOR_OPT_PARALLEL_OK);
+		else
+			exec_prepare_plan(estate, expr, 0);
+
 		stmt->mod_stmt = false;
 		foreach(l, SPI_plan_get_plan_sources(expr->plan))
 		{
@@ -3869,8 +3874,13 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 										 estate->readonly_func, 0);
 	}
 	else
-		exec_res = SPI_execute(querystr, estate->readonly_func, 0);
-
+	{
+		/* Allow parallelism if the function is not trigger type. */
+		if (estate->func->fn_is_trigger == PLPGSQL_NOT_TRIGGER)
+			exec_res = SPI_execute(querystr, estate->readonly_func, CURSOR_OPT_PARALLEL_OK);
+		else
+			exec_res = SPI_execute(querystr, estate->readonly_func, 0);
+	}
 	switch (exec_res)
 	{
 		case SPI_OK_SELECT:
@@ -5172,8 +5182,13 @@ 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);
-
+	{
+		/* Allow parallelism is the function is not trigger type. */
+		if (estate->func->fn_is_trigger == PLPGSQL_NOT_TRIGGER)
+			exec_prepare_plan(estate, expr, CURSOR_OPT_PARALLEL_OK);
+		else
+			exec_prepare_plan(estate, expr, 0);
+	}
 	/*
 	 * If this is a simple expression, bypass SPI and use the executor
 	 * directly
@@ -5183,9 +5198,14 @@ exec_eval_expr(PLpgSQL_execstate *estate,
 		return result;
 
 	/*
-	 * Else do it the hard way via exec_run_select
+	 * Else do it the hard way via exec_run_select. Enable parallelism
+	 * if function is not trigger type.
 	 */
-	rc = exec_run_select(estate, expr, 2, NULL, false);
+	if (estate->func->fn_is_trigger == PLPGSQL_NOT_TRIGGER)
+		rc = exec_run_select(estate, expr, 2, NULL, true);
+	else
+		rc = exec_run_select(estate, expr, 2, NULL, false);
+
 	if (rc != SPI_OK_SELECT)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),