The main purpose for the configuration of HIVE_SUPPORT_SQL11_RESERVED_KEYWORDS is for backward compatibility because a lot of reserved key words has been used as identifiers in the previous releases. We already have had several releases with this configuration. Now when I tried to add new set operators to the parser, ANTLR is always complaining "code too large". I think it is time to remove this configuration. (1) It will simplify the parser logic and largely reduce the size of generated parser code; (2) it leave space for new features, especially those which require parser changes.