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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