Function SearchSysCacheAttNum

src/backend/utils/cache/syscache.c:1559–1575

* SearchSysCacheAttNum * * This routine is equivalent to SearchSysCache on the ATTNUM cache, * except that it will return NULL if the found attribute is marked * attisdropped. This is convenient for callers that want to act as * though dropped attributes don't exist. */

 * though dropped attributes don't exist.
 */
HeapTuple
SearchSysCacheAttNum(Oid relid, int16 attnum)
{
	HeapTuple	tuple;

	tuple = SearchSysCache2(ATTNUM,
							ObjectIdGetDatum(relid),
							Int16GetDatum(attnum));
	if (!HeapTupleIsValid(tuple))
		return NULL;
	if (((Form_pg_attribute) GETSTRUCT(tuple))->attisdropped)
	{
		ReleaseSysCache(tuple);
		return NULL;
	}
	return tuple;
}

/*
 * SearchSysCacheCopyAttNum