Adam Szita created HIVE-21217:
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Summary: Optimize range calculation for PTF
Key: HIVE-21217
URL: https://issues.apache.org/jira/browse/HIVE-21217
Project: Hive
Issue Type: Improvement
Reporter: Adam Szita
Assignee: Adam Szita
During window function execution Hive has to iterate on neighbouring rows of
the current row to find the beginning and end of the proper range (on which the
aggregation will be executed).
When we're using range based windows and have many rows with a certain key
value this can take a lot of time. (e.g. partition size of 80M, in which we
have 2 ranges of 40M rows according to the orderby column: within these 40M
rowsets we're doing 40M x 40M/2 steps.. which is of n^2 time complexity)
I propose to introduce a cache that keeps track of already calculated range
ends so it can be reused in future scans.
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