[jira] [Updated] (FLINK-19830) Properly implements processing-time temporal table join

["Yun Gao (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-19830?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yun Gao updated FLINK-19830:
----------------------------
    Fix Version/s: 1.16.0

> Properly implements processing-time temporal table join
> -------------------------------------------------------
>
>                 Key: FLINK-19830
>                 URL: https://issues.apache.org/jira/browse/FLINK-19830
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table SQL / Runtime
>            Reporter: Leonard Xu
>            Assignee: Leonard Xu
>            Priority: Major
>             Fix For: 1.15.0, 1.16.0
>
>
> The exsiting TemporalProcessTimeJoinOperator has already supported temporal table join.
>  However, the semantic of this implementation is problematic, because the join processing for left stream doesn't wait for the complete snapshot of temporal table, this may mislead users in production environment.
> Under the processing time temporal join semantics, to get the complete snapshot of temporal table may need introduce new mechanism in FLINK SQL in the future.
> **Background** : 
>  * The reason why we turn off the switch[1] for `FOR SYSTEM_TIME AS OF` syntax for *temporal table join* is only the semantic consideration as above.
>  * The reason why we turn on *temporal table function*  is that it has been alive for a long time, thus although it exists same semantic problem, but we still support it from the perspective of compatibility.
> [1] [https://github.com/apache/flink/blob/4fe9f525a92319acc1e3434bebed601306f7a16f/flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/nodes/exec/stream/StreamExecTemporalJoin.java#L257]



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