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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-6430) MapJoin hash table has large memory overhead
Date Thu, 24 Apr 2014 03:34:15 GMT

    [ https://issues.apache.org/jira/browse/HIVE-6430?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13979238#comment-13979238
] 

Gopal V commented on HIVE-6430:
-------------------------------

That comment above probably didn't parse - but the usage of lazy keys make it impossible to
generate a min-max range (or >1 ranges) from the hashtable.

> MapJoin hash table has large memory overhead
> --------------------------------------------
>
>                 Key: HIVE-6430
>                 URL: https://issues.apache.org/jira/browse/HIVE-6430
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>         Attachments: HIVE-6430.01.patch, HIVE-6430.02.patch, HIVE-6430.03.patch, HIVE-6430.04.patch,
HIVE-6430.05.patch, HIVE-6430.06.patch, HIVE-6430.07.patch, HIVE-6430.08.patch, HIVE-6430.09.patch,
HIVE-6430.patch
>
>
> Right now, in some queries, I see that storing e.g. 4 ints (2 for key and 2 for row)
can take several hundred bytes, which is ridiculous. I am reducing the size of MJKey and MJRowContainer
in other jiras, but in general we don't need to have java hash table there.  We can either
use primitive-friendly hashtable like the one from HPPC (Apache-licenced), or some variation,
to map primitive keys to single row storage structure without an object per row (similar to
vectorization).



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