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From "Jitendra Nath Pandey (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-6664) Vectorized variance computation differs from row mode computation.
Date Mon, 17 Mar 2014 22:14:56 GMT

     [ https://issues.apache.org/jira/browse/HIVE-6664?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jitendra Nath Pandey updated HIVE-6664:
---------------------------------------

       Resolution: Fixed
    Fix Version/s: 0.13.0
           Status: Resolved  (was: Patch Available)

> 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
>             Fix For: 0.13.0
>
>         Attachments: HIVE-6664.1.patch, HIVE-6664.1.patch, 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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