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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-562) join does not work well if there is a very large skew in keys
Date Thu, 22 Oct 2009 15:38:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12768720#action_12768720
] 

Namit Jain commented on HIVE-562:
---------------------------------

That will also work - but we dont know the number of rows before hand for a given key.
We can have some hueristics, based on which, a persistent storage can be used

> join does not work well if there is a very large skew in keys
> -------------------------------------------------------------
>
>                 Key: HIVE-562
>                 URL: https://issues.apache.org/jira/browse/HIVE-562
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>    Affects Versions: 0.4.0
>            Reporter: Namit Jain
>
> Only the last table is streamed in case of regular joins.
> So, for any other table, or for any small table (in case of map-joins), if the number
of values for a given key are very large, it does not scale.

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