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https://issues.apache.org/jira/browse/SPARK-32863?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jungtaek Lim reassigned SPARK-32863:
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Assignee: Cheng Su
> Full outer stream-stream join
> -----------------------------
>
> Key: SPARK-32863
> URL: https://issues.apache.org/jira/browse/SPARK-32863
> Project: Spark
> Issue Type: Sub-task
> Components: Structured Streaming
> Affects Versions: 3.1.0
> Reporter: Cheng Su
> Assignee: Cheng Su
> Priority: Major
>
> 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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