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https://issues.apache.org/jira/browse/HIVE-21217?focusedWorklogId=199264&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-199264
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ASF GitHub Bot logged work on HIVE-21217:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 15/Feb/19 14:40
Start Date: 15/Feb/19 14:40
Worklog Time Spent: 10m
Work Description: szlta commented on pull request #538: HIVE-21217:
Optimize range calculation for PTF
URL: https://github.com/apache/hive/pull/538
@pvary
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Issue Time Tracking
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Worklog Id: (was: 199264)
Time Spent: 10m
Remaining Estimate: 0h
> 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
> Priority: Major
> Labels: pull-request-available
> Attachments: HIVE-21217.0.patch, HIVE-21217.1.patch,
> HIVE-21217.2.patch
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> 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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