[jira] [Assigned] (FLINK-19870) Fix special case when the reuse of exchange causes the deadlock

["godfrey he (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-19870?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

godfrey he reassigned FLINK-19870:
----------------------------------

    Assignee: Caizhi Weng

> Fix special case when the reuse of exchange causes the deadlock
> ---------------------------------------------------------------
>
>                 Key: FLINK-19870
>                 URL: https://issues.apache.org/jira/browse/FLINK-19870
>             Project: Flink
>          Issue Type: Bug
>          Components: Table SQL / Planner
>            Reporter: Caizhi Weng
>            Assignee: Caizhi Weng
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.12.0
>
>
> Currently the reuse of exchange is not considered to be a deadlock because although the exec node of an exchange is reused, its underlying transformation is not reused. However if this behavior changes a deadlock may occur.
> For example, consider the following SQL and its plan:
> {code:sql}
> WITH T1 AS (SELECT a FROM x)
> SELECT * FROM T1
>   INNER JOIN T1 AS T2 ON T1.a = T2.a
> {code}
> {code}
> HashJoin(joinType=[InnerJoin], where=[=(a, a0)], select=[a, a0], build=[right])
> :- Exchange(distribution=[hash[a]], shuffle_mode=[BATCH], reuse_id=[1])
> :  +- Calc(select=[a])
> :     +- LegacyTableSourceScan(table=[[default_catalog, default_database, x, source: [TestTableSource(a, b, c)]]], fields=[a, b, c])
> +- Reused(reference_id=[1])
> {code}
> The reuse of exchange may cause a deadlock on hash join.



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