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Posted to dev@hive.apache.org by "Zoltan Haindrich (JIRA)" <ji...@apache.org> on 2018/06/07 12:46:00 UTC

[jira] [Created] (HIVE-19824) Improve online datasize estimations for MapJoins

Zoltan Haindrich created HIVE-19824:
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             Summary: Improve online datasize estimations for MapJoins
                 Key: HIVE-19824
                 URL: https://issues.apache.org/jira/browse/HIVE-19824
             Project: Hive
          Issue Type: Improvement
            Reporter: Zoltan Haindrich
            Assignee: Zoltan Haindrich


Statistics.datasize() only accounts for "real" data size; but for example handling 1M rows might introduce some datastructure overhead...if the "real" data is small - even this overhead might become the real memory usage

for 6.5M rows of (int,int) the estimation is 52MB
in reality this eats up ~260MB from which 210MB is used to service the hashmap functionality to that many rows.



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