Function scanNameSpaceForRelid

src/backend/parser/parse_relation.c:225–259

* Search the query's table namespace for a relation item matching the * given relation OID. Return the nsitem if a unique match, or NULL * if no match. Raise error if multiple matches. * * See the comments for refnameNamespaceItem to understand why this * acts the way it does. */

 * acts the way it does.
 */
static ParseNamespaceItem *
scanNameSpaceForRelid(ParseState *pstate, Oid relid, int location)
{
	ParseNamespaceItem *result = NULL;
	ListCell   *l;

	foreach(l, pstate->p_namespace)
	{
		ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(l);
		RangeTblEntry *rte = nsitem->p_rte;

		/* Ignore columns-only items */
		if (!nsitem->p_rel_visible)
			continue;
		/* If not inside LATERAL, ignore lateral-only items */
		if (nsitem->p_lateral_only && !pstate->p_lateral_active)
			continue;

		/* yes, the test for alias == NULL should be there... */
		if (rte->rtekind == RTE_RELATION &&
			rte->relid == relid &&
			rte->alias == NULL)
		{
			if (result)
				ereport(ERROR,
						(errcode(ERRCODE_AMBIGUOUS_ALIAS),
						 errmsg("table reference %u is ambiguous",
								relid),
						 parser_errposition(pstate, location)));
			check_lateral_ref_ok(pstate, nsitem, location);
			result = nsitem;
		}
	}
	return result;
}

/*
 * Search the query's CTE namespace for a CTE matching the given unqualified