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From "Lefty Leverenz (JIRA)" <>
Subject [jira] [Commented] (HIVE-6429) MapJoinKey has large memory overhead in typical cases
Date Mon, 30 Jun 2014 00:33:28 GMT


Lefty Leverenz commented on HIVE-6429:

Added comment to HIVE-6586 so the description of *hive.mapjoin.optimized.keys* won't get lost
in the shuffle when HIVE-6037 changes

> MapJoinKey has large memory overhead in typical cases
> -----------------------------------------------------
>                 Key: HIVE-6429
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>             Fix For: 0.13.0
>         Attachments: HIVE-6429.01.patch, HIVE-6429.02.patch, HIVE-6429.03.patch, HIVE-6429.04.patch,
HIVE-6429.05.patch, HIVE-6429.06.patch, HIVE-6429.07.patch, HIVE-6429.08.patch, HIVE-6429.09.patch,
HIVE-6429.10.patch, HIVE-6429.WIP.patch, HIVE-6429.patch
> The only thing that MJK really needs it hashCode and equals (well, and construction),
so there's no need to have array of writables in there. Assuming all the keys for a table
have the same structure, for the common case where keys are primitive types, we can store
something like a byte array combination of keys to reduce the memory usage. Will probably
speed up compares too.

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