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https://issues.apache.org/jira/browse/HIVE-6664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13934793#comment-13934793
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Jitendra Nath Pandey commented on HIVE-6664:
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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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