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Posted to issues@flink.apache.org by "godfrey he (Jira)" <ji...@apache.org> on 2019/12/02 03:30:00 UTC

[jira] [Commented] (FLINK-15004) Choose SortMergeJoin instead of HashJoin if the statistics is unknown

    [ https://issues.apache.org/jira/browse/FLINK-15004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16985790#comment-16985790 ] 

godfrey he commented on FLINK-15004:
------------------------------------

i would like to take this ticket

> Choose SortMergeJoin instead of HashJoin if the statistics is unknown
> ---------------------------------------------------------------------
>
>                 Key: FLINK-15004
>                 URL: https://issues.apache.org/jira/browse/FLINK-15004
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table SQL / Planner
>    Affects Versions: 1.9.0, 1.9.1
>            Reporter: godfrey he
>            Priority: Major
>             Fix For: 1.10.0
>
>
> Currently, blink planner will use default rowCount value (defined in {{FlinkPreparingTableBase#DEFAULT_ROWCOUNT}} ) when the statistics is unknown, and maybe choose {{HashJoin}} instead of {{SortMergeJoin}}. The job will hang if the build side has huge input size. So It's better to use {{SortMergeJoin}} for execution stability if the statistics is unknown.



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