[jira] Updated: (HIVE-609) optimize multi-group by

["Namit Jain (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-609?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Namit Jain updated HIVE-609:
----------------------------

    Attachment: hive.609.1.patch

> optimize multi-group by 
> ------------------------
>
>                 Key: HIVE-609
>                 URL: https://issues.apache.org/jira/browse/HIVE-609
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: hive.609.1.patch
>
>
> For query like:
> from src
> insert overwrite table dest1 select col1, count(distinct colx) group by col1
> insert overwrite table dest2 select col2, count(distinct colx) group by col2;
> If map side aggregation is turned off, we currently do 4 map-reduce jobs.
> The plan can be optimized by running it in 3 map-reduce jobs, by spraying over the
> distinct column first and then aggregating individual results.
> This may not be possible if there are multiple distinct columns, but the above query is very common
> in data warehousing environments.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.