Make AT keyword non-reserved
@@ -434,6 +434,7 @@ nonReserved
: SHOW | TABLES | COLUMNS | COLUMN | PARTITIONS | FUNCTIONS | SCHEMAS | CATALOGS | SESSION
| ADD
| FILTER
+ | AT
| OVER | PARTITION | RANGE | ROWS | PRECEDING | FOLLOWING | CURRENT | ROW | MAP | ARRAY
| TINYINT | SMALLINT | INTEGER | DATE | TIME | TIMESTAMP | INTERVAL | ZONE
| YEAR | MONTH | DAY | HOUR | MINUTE | SECOND
