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Posted to dev@hive.apache.org by "Jitendra Nath Pandey (JIRA)" <ji...@apache.org> on 2014/03/14 08:08:06 UTC

[jira] [Created] (HIVE-6664) Vectorized variance computation differs from row mode computation.

Jitendra Nath Pandey created HIVE-6664:
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             Summary: Vectorized variance computation differs from row mode computation.
                 Key: HIVE-6664
                 URL: https://issues.apache.org/jira/browse/HIVE-6664
             Project: Hive
          Issue Type: Bug
            Reporter: Jitendra Nath Pandey
            Assignee: Jitendra Nath Pandey


Following query can show the difference:
select count(ss_sales_price), sum(ss_sales_price), avg(ss_sales_price), var_samp(ss_sales_price), var_pop(ss_sales_price), stddev_pop(ss_sales_price), stddev_samp(ss_sales_price) from store_sales

The reason for the difference is that row mode converts the decimal value to double upfront to calculate sum of values. But the vector mode performs local aggregate sum as decimal and converts into double only at flush.



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