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Posted to issues@hive.apache.org by "ASF GitHub Bot (Jira)" <ji...@apache.org> on 2022/05/09 22:11:00 UTC

[jira] [Work logged] (HIVE-26009) Determine number of buckets for implicitly bucketed ACIDv2 tables

     [ https://issues.apache.org/jira/browse/HIVE-26009?focusedWorklogId=768207&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-768207 ]

ASF GitHub Bot logged work on HIVE-26009:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 09/May/22 22:10
            Start Date: 09/May/22 22:10
    Worklog Time Spent: 10m 
      Work Description: simhadri-g closed pull request #3224: HIVE-26009: Determine number of buckets for implicitly bucketed ACIDv…
URL: https://github.com/apache/hive/pull/3224




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

    Worklog Id:     (was: 768207)
    Time Spent: 20m  (was: 10m)

> Determine number of buckets for implicitly bucketed ACIDv2 tables 
> ------------------------------------------------------------------
>
>                 Key: HIVE-26009
>                 URL: https://issues.apache.org/jira/browse/HIVE-26009
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Simhadri G
>            Assignee: Simhadri G
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Hive tries to set number of reducers equal to number of buckets here: 
> [https://github.com/apache/hive/blob/9857c4e584384f7b0a49c34bc2bdf876c2ea1503/ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java#L6958] 
>  
> The numberOfBuckets for implicitly bucketed tables is set to -1 by default. When this is the case, it is left to hive to estimate the number of reducers required the job, based on job input, and configuration parameters.
> [https://github.com/apache/hive/blob/9857c4e584384f7b0a49c34bc2bdf876c2ea1503/ql/src/java/org/apache/hadoop/hive/ql/exec/Utilities.java#L3369]
>  
> This estimate is not optimal in all cases. In the worst case, it case result in a single reducer being launched , which can lead to a significant bottleneck in performance .
>  
> Ideally,  the number of reducers launched should equal to number of buckets, which is the case for explicitly bucketed tables.
>  
>  



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