ayushtkn opened a new pull request, #3142:
URL: https://github.com/apache/hive/pull/3142

   After https://issues.apache.org/jira/browse/HIVE-23530 , almost all compute 
stats functions are vectorizable. Only function that is not vectorizable is 
"compute_bit_vector" for ndv statistics computation. This causes "create table 
as select" and "insert overwrite select" queries to run in non-vectorized mode. 
   
   Even a very naive implementation of vectorized compute_bit_vector gives 
about 50% performance improvement on simple "insert overwrite select" queries. 
That is because entire mapper or reducer can run in vectorized mode.


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