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https://issues.apache.org/jira/browse/FLINK-2107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14662050#comment-14662050
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Chiwan Park commented on FLINK-2107:
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Hi, I'm working on this issue. I have a question about implementation of hash
based join.
In {{NonReusingBuildFirstHashMatchIterator.callWithNextKey}}, there are 3
points to call join function by fetching first value, second value, and remain
values. Is there a purpose about this? Why the calling points are split?
> Implement Hash Outer Join algorithm
> -----------------------------------
>
> Key: FLINK-2107
> URL: https://issues.apache.org/jira/browse/FLINK-2107
> Project: Flink
> Issue Type: Sub-task
> Components: Local Runtime
> Reporter: Fabian Hueske
> Assignee: Chiwan Park
> Priority: Minor
> Fix For: pre-apache
>
>
> Flink does not natively support outer joins at the moment.
> This issue proposes to implement a hash outer join algorithm that can cover
> left and right outer joins.
> The implementation can be based on the regular hash join iterators (for
> example `ReusingBuildFirstHashMatchIterator` and
> `NonReusingBuildFirstHashMatchIterator`, 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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