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From "ASF GitHub Bot (Jira)" <j...@apache.org>
Subject [jira] [Work logged] (HIVE-24234) Improve checkHashModeEfficiency in VectorGroupByOperator
Date Tue, 13 Oct 2020 00:12:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-24234?focusedWorklogId=499747&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-499747
]

ASF GitHub Bot logged work on HIVE-24234:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 13/Oct/20 00:11
            Start Date: 13/Oct/20 00:11
    Worklog Time Spent: 10m 
      Work Description: ashutoshc commented on pull request #1560:
URL: https://github.com/apache/hive/pull/1560#issuecomment-707408314


   +1 LGTM


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 499747)
    Time Spent: 20m  (was: 10m)

> Improve checkHashModeEfficiency in VectorGroupByOperator
> --------------------------------------------------------
>
>                 Key: HIVE-24234
>                 URL: https://issues.apache.org/jira/browse/HIVE-24234
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Rajesh Balamohan
>            Assignee: Rajesh Balamohan
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HIVE-24234.wip.patch
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Currently, {{VectorGroupByOperator::checkHashModeEfficiency}} compares the number of
entries with the number input records that have been processed. For grouping sets, it accounts
for grouping set length as well.
> Issue is that, the condition becomes invalid after processing large number of input records.
This prevents the system from switching over to streaming mode. 
> e.g Assume 500,000 input records processed, with 9 grouping sets, with 100,000 entries
in hashtable. Hashtable would never cross 4,500,0000 entries as the max size itself is 1M
by default. 
> It would be good to compare the input records (adjusted for grouping sets) with number
of output records (along with size of hashtable size) to determine hashing or streaming mode.
> E.g Q67.



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