[jira] [Commented] (FLINK-7800) Enable window joins without equi-join predicates

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

    [ https://issues.apache.org/jira/browse/FLINK-7800?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16216573#comment-16216573 ] 

Xingcan Cui commented on FLINK-7800:
------------------------------------

Hi [~fhueske], thanks for opening this. I got a question about the join validation. Why couldn't we "push down" all these checks (e.g., for equi-join predicate) into the DataStream/DataSet rules and organize them in a flat mode?

> Enable window joins without equi-join predicates
> ------------------------------------------------
>
>                 Key: FLINK-7800
>                 URL: https://issues.apache.org/jira/browse/FLINK-7800
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>    Affects Versions: 1.4.0
>            Reporter: Fabian Hueske
>            Assignee: Xingcan Cui
>
> Currently, windowed joins can only be translated if they have at least on equi-join predicate. This limitation exists due to the lack of a good cross join strategy for the DataSet API.
> Due to the window, windowed joins do not have to be executed as cross joins. Hence, the equi-join limitation does not need to be enforces (even though non-equi joins are executed with a parallelism of 1 right now).
> We can resolve this issue by adding a boolean flag to the {{FlinkLogicalJoinConverter}} rule to permit non-equi joins and add such a rule to the logical optimization set of the DataStream API.



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