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https://issues.apache.org/jira/browse/FLINK-2105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14601254#comment-14601254
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Chiwan Park commented on FLINK-2105:
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Hi [~r-pogalz],
I think that this issue covers only implementation of Iterators not
integration. FLINK-687 should cover the integration with Drivers and optimizers.
We need a new Driver because outer-join returns a different result from
equi-join (MatchDriver). But the Driver is not for sort-merge based outer-join
only. Hash-based outer-join will use the same Driver. If I understand
correctly, A Driver returns a same result although the strategy is different.
> Implement Sort-Merge Outer Join algorithm
> -----------------------------------------
>
> Key: FLINK-2105
> URL: https://issues.apache.org/jira/browse/FLINK-2105
> Project: Flink
> Issue Type: Sub-task
> Components: Local Runtime
> Reporter: Fabian Hueske
> Assignee: Ricky Pogalz
> Priority: Minor
> Fix For: pre-apache
>
>
> Flink does not natively support outer joins at the moment.
> This issue proposes to implement a sort-merge outer join algorithm that can
> cover left, right, and full outer joins.
> The implementation can be based on the regular sort-merge join iterator
> ({{ReusingMergeMatchIterator}} and {{NonReusingMergeMatchIterator}}, see also
> {{MatchDriver}} class)
> The Reusing and NonReusing variants differ in whether object instances are
> reused or new objects are created. I would start with the NonReusing variant
> which is safer from a user's point of view and should also be easier to
> implement.
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