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From "Wei Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-13809) Hybrid Grace Hash Join memory usage estimation didn't take into account the bloom filter size
Date Fri, 20 May 2016 21:41:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-13809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15294295#comment-15294295
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Wei Zheng commented on HIVE-13809:
----------------------------------

OK, agree. Btw,
{code}
Estimated small table size: 1600000000
{code}
This is data size (in bytes), not number of keys. Estimated number of keys is 266666672 (still
a big number).

> Hybrid Grace Hash Join memory usage estimation didn't take into account the bloom filter
size
> ---------------------------------------------------------------------------------------------
>
>                 Key: HIVE-13809
>                 URL: https://issues.apache.org/jira/browse/HIVE-13809
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>    Affects Versions: 2.0.0, 2.1.0
>            Reporter: Wei Zheng
>            Assignee: Wei Zheng
>
> Memory estimation is important during hash table loading, because we need to make the
decision of whether to load the next hash partition in memory or spill it. If the assumption
is there's enough memory but it turns out not the case, we will run into OOM problem.
> Currently hybrid grace hash join memory usage estimation didn't take into account the
bloom filter size. In large test cases (TB scale) the bloom filter grows as big as hundreds
of MB, big enough to cause estimation error.
> The solution is to count in the bloom filter size into memory estimation.



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