Handling of CURRENT_TIMESTAMP output format

The output format of the CURRENT_TIMESTAMP user defined function (UDF) is inconsistent in certain scenarios.

Before upgrade to CDP

CURRENT_TIMESTAMP returns the result in different output formats. For example,
select current_timestamp();
2016-04-14 18:26:58.875

select current_timestamp() from all100k union select current_timestamp() from over100k limit 5;
2016-04-14 18:29:56

In the second query, the fractional seconds precision is removed from the output.

After upgrade to CDP

HIVE-13837 fixes this issue and the output format for CURRENT_TIMESTAMP YYYY-MM-DD HH:MM:SS.fff.