hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jitendra Nath Pandey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-6664) Vectorized variance computation differs from row mode computation.
Date Fri, 14 Mar 2014 09:03:48 GMT

    [ 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.



--
This message was sent by Atlassian JIRA
(v6.2#6252)

Mime
View raw message