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Posted to dev@hive.apache.org by "Zoltan Haindrich (JIRA)" <ji...@apache.org> on 2018/06/07 10:52:00 UTC

[jira] [Created] (HIVE-19823) BytesBytesMultiHashMap estimation should account for load size

Zoltan Haindrich created HIVE-19823:
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             Summary: BytesBytesMultiHashMap estimation should account for load size
                 Key: HIVE-19823
                 URL: https://issues.apache.org/jira/browse/HIVE-19823
             Project: Hive
          Issue Type: Improvement
            Reporter: Zoltan Haindrich
            Assignee: Zoltan Haindrich


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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