[jira] [Commented] (TEZ-2956) Handle auto-reduce parallelism when the totalNumBipartiteSourceTasks is 0

["TezQA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TEZ-2956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15015225#comment-15015225 ] 

TezQA commented on TEZ-2956:
----------------------------

{color:green}+1 overall{color}.  Here are the results of testing the latest attachment
  http://issues.apache.org/jira/secure/attachment/12773433/TEZ-2956.1.patch
  against master revision 4561b82.

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:green}+1 tests included{color}.  The patch appears to include 1 new or modified test files.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version 3.0.1) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number of release audit warnings.

    {color:green}+1 core tests{color}.  The patch passed unit tests in .

Test results: https://builds.apache.org/job/PreCommit-TEZ-Build/1328//testReport/
Console output: https://builds.apache.org/job/PreCommit-TEZ-Build/1328//console

This message is automatically generated.

> Handle auto-reduce parallelism when the totalNumBipartiteSourceTasks is 0
> -------------------------------------------------------------------------
>
>                 Key: TEZ-2956
>                 URL: https://issues.apache.org/jira/browse/TEZ-2956
>             Project: Apache Tez
>          Issue Type: Bug
>            Reporter: Rajesh Balamohan
>            Assignee: Rajesh Balamohan
>         Attachments: TEZ-2956.1.patch, TEZ-2956_DAG.png, With_Patch.png, Without_Patch.png
>
>
> In certain cases (e.g M --> R --> R), if the parent vertex has 0 tasks tez currently does not modify the parallelism factor in downstream.
> e.g
> {noformat}
> SELECT ss_store_sk,
>        ss_sold_date_sk,
>        ss_quantity,
>        ss_sales_price,
>        LEAD(ss_sales_price, 1) OVER(PARTITION BY ss_store_sk
>                                     ORDER BY ss_quantity)
> FROM store_sales
> WHERE ss_sold_date_sk IS NOT NULL
>   AND ss_quantity IS NOT NULL
>   AND ss_sales_price > 2857684
>   AND ss_sales_price < 2857685
>   AND ss_store_sk > 10234233423
>   AND ss_store_sk < 20234234324
> ORDER BY ss_store_sk,
>          ss_sold_date_sk;
> {noformat}
> This would launch DAG "M1 (0) --> R2 (156) --> R3 (1)".  However, R2 retains the parallelism of 156 even though no output would be generated in M1. 



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