Function querytree_safe_for_qe_walker

src/backend/executor/functions.c:178–243

static void sqlfunction_destroy(DestReceiver *self);

static bool
querytree_safe_for_qe_walker(Node *expr, void *context)
{
	Assert(context == NULL);
	
	if (!expr)
	{
		/**
		 * Do not end recursion just because we have reached one leaf node.
		 */
		return false;
	}

	switch(nodeTag(expr))
	{
		case T_Query:
			{
				Query *q = (Query *) expr;
				
				if (!allow_segment_DML &&
					(q->commandType != CMD_SELECT
					 || (q->utilityStmt != NULL &&
					     IsA(q->utilityStmt, CreateTableAsStmt))
					 || q->resultRelation > 0))
				{
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("function cannot execute on a QE slice because it issues a non-SELECT statement")));
				}
				
				ListCell * f = NULL;
				foreach(f,q->rtable)
				{
					RangeTblEntry *rte = (RangeTblEntry *) lfirst(f);

					if (rte->rtekind == RTE_RELATION)
					{
						Assert(rte->relid != InvalidOid);
						
						Oid namespaceId = get_rel_namespace(rte->relid);

						Assert(namespaceId != InvalidOid);
						
						if (!(IsCatalogNamespace(namespaceId) ||
									IsToastNamespace(namespaceId) ||
									IsAoSegmentNamespace(namespaceId) ||
									(IsReplicatedTable(rte->relid) &&
									 !IS_QUERY_DISPATCHER())))
						{
							ereport(ERROR,
									(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
									 errmsg("function cannot execute on a QE slice because it accesses relation \"%s.%s\"",
											quote_identifier(get_namespace_name(namespaceId)),
											quote_identifier(get_rel_name(rte->relid)))));
						}
					}
				}
				query_tree_walker(q, querytree_safe_for_qe_walker, context, 0);