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Posted to issues@hive.apache.org by "Zoltan Haindrich (JIRA)" <ji...@apache.org> on 2018/06/07 12:46:00 UTC
[jira] [Assigned] (HIVE-19824) Improve online datasize estimations
for MapJoins
[ https://issues.apache.org/jira/browse/HIVE-19824?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Zoltan Haindrich reassigned HIVE-19824:
---------------------------------------
> 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
> Priority: Major
>
> 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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