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

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

     [ https://issues.apache.org/jira/browse/TEZ-2956?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bikas Saha updated TEZ-2956:
----------------------------
    Fix Version/s: 0.7.1

> 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
>             Fix For: 0.7.1, 0.8.2
>
>         Attachments: TEZ-2956.1.patch, TEZ-2956.2.patch, TEZ-2956.3.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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