[jira] [Commented] (HIVE-19823) BytesBytesMultiHashMap estimation should account for loadFactor

["Zoltan Haindrich (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-19823?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16505989#comment-16505989 ] 

Zoltan Haindrich commented on HIVE-19823:
-----------------------------------------

[~sershe] Could you please take a look?

> BytesBytesMultiHashMap estimation should account for loadFactor
> ---------------------------------------------------------------
>
>                 Key: HIVE-19823
>                 URL: https://issues.apache.org/jira/browse/HIVE-19823
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Zoltan Haindrich
>            Assignee: Zoltan Haindrich
>            Priority: Major
>         Attachments: HIVE-19823.01.patch
>
>
> it could happen that the capacity is known beforehand; and the estimated size of the hashtable is accurate; but still because after some time the element count violates loadfactor ration a rehash will occur.
> this by default could happen with a {{1-loadfactor = 25%}}  probability
> https://github.com/apache/hive/blob/cfd57348c1ac188e0ba131d5636a62ff7b7c27be/ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/BytesBytesMultiHashMap.java#L176-L187



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