FIX BUGS:
1.Fix some bugs in fill query for super table.
2.Fix the crash while executing "show variables" command.
3.Fix JDBC memory leak whiling invoking the C native library.
4.The default output column name for arithmetic expression is set to the original user input.
5.Add some checks for memory allocation failure.

NEW FEATURES:
1.The constant value column in select clause is supported.
2.The binary tags can be used as the join query condition for super tables.

ENHANCEMENTS:
1.Optimized the last_row query performance.
2.Reducing the memory consumptions during the time interval query.