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

["Jitendra Nath Pandey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-6664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13934793#comment-13934793 ] 

Jitendra Nath Pandey commented on HIVE-6664:
--------------------------------------------

Review board : https://reviews.apache.org/r/19216/

> 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
>         Attachments: HIVE-6664.1.patch
>
>
> Following query can show the difference:
> select  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, when computing variance. But the vector mode performs local aggregate sum as decimal and converts into double only at flush.



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