Function ExecGetRangeTableRelation

src/backend/executor/execUtils.c:838–881

* ExecGetRangeTableRelation * Open the Relation for a range table entry, if not already done * * The Relations will be closed again in ExecEndPlan(). */

 * The Relations will be closed again in ExecEndPlan().
 */
Relation
ExecGetRangeTableRelation(EState *estate, Index rti)
{
	Relation	rel;

	Assert(rti > 0 && rti <= estate->es_range_table_size);

	rel = estate->es_relations[rti - 1];
	if (rel == NULL)
	{
		/* First time through, so open the relation */
		RangeTblEntry *rte = exec_rt_fetch(rti, estate);

		Assert(rte->rtekind == RTE_RELATION);

		/* GPDB: a QE process is not holding the locks yet, same as a parallel worker. */
		if (!IsParallelWorker() && Gp_role != GP_ROLE_EXECUTE)
		{
			/*
			 * In a normal query, we should already have the appropriate lock,
			 * but verify that through an Assert.  Since there's already an
			 * Assert inside table_open that insists on holding some lock, it
			 * seems sufficient to check this only when rellockmode is higher
			 * than the minimum.
			 */
			rel = table_open(rte->relid, NoLock);
			Assert(rte->rellockmode == AccessShareLock ||
				   CheckRelationLockedByMe(rel, rte->rellockmode, false));
		}
		else
		{
			/*
			 * If we are a parallel worker, we need to obtain our own local
			 * lock on the relation.  This ensures sane behavior in case the
			 * parent process exits before we do.
			 */
			rel = table_open(rte->relid, rte->rellockmode);
		}

		estate->es_relations[rti - 1] = rel;
	}

	return rel;
}

/*
 * ExecInitResultRelation