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From "Cheng Su (Jira)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-32863) Full outer stream-stream join
Date Sat, 12 Sep 2020 07:53:00 GMT

    [ https://issues.apache.org/jira/browse/SPARK-32863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17194646#comment-17194646
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Cheng Su commented on SPARK-32863:
----------------------------------

Will raise a PR in next couple of weeks. Thanks.

> Full outer stream-stream join
> -----------------------------
>
>                 Key: SPARK-32863
>                 URL: https://issues.apache.org/jira/browse/SPARK-32863
>             Project: Spark
>          Issue Type: New Feature
>          Components: Structured Streaming
>    Affects Versions: 3.1.0
>            Reporter: Cheng Su
>            Priority: Trivial
>
> Current stream-stream join supports inner, left outer and right outer join ([https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/StreamingSymmetricHashJoinExec.scala#L166] ).
With current design of stream-stream join (which marks whether the row is matched or not in
state store), it would be very easy to support full outer join as well.
>  
> Full outer stream-stream join will work as followed:
> (1).for left side input row, check if there's a match on right side state store. If there's
a match, output all matched rows. Put the row in left side state store.
> (2).for right side input row, check if there's a match on left side state store. If there's
a match, output all matched rows and update left side rows state with "matched" field to set
to true. Put the right side row in right side state store.
> (3).for left side row needs to be evicted from state store, output the row if "matched"
field is false.
> (4).for right side row needs to be evicted from state store, output the row if "matched"
field is false.



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