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https://issues.apache.org/jira/browse/FLINK-3910?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Greg Hogan closed FLINK-3910.
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Resolution: Duplicate
> New self-join operator
> ----------------------
>
> Key: FLINK-3910
> URL: https://issues.apache.org/jira/browse/FLINK-3910
> Project: Flink
> Issue Type: New Feature
> Components: DataSet API, Java API, Scala API
> Affects Versions: 1.1.0
> Reporter: Greg Hogan
> Assignee: Greg Hogan
>
> Flink currently provides inner- and outer-joins as well as cogroup and the
> non-keyed cross. {{JoinOperator}} hints at future support for semi- and
> anti-joins.
> Many Gelly algorithms perform a self-join [0]. Still pending reviews,
> FLINK-3768 performs a self-join on non-skewed data in TriangleListing.java
> and FLINK-3780 performs a self-join on skewed data in JaccardSimilarity.java.
> A {{SelfJoinHint}} will select between skewed and non-skewed implementations.
> The object-reuse-disabled case can be simply handled with a new {{Operator}}.
> The object-reuse-enabled case requires either {{CopyableValue}} types (as in
> the code above) or a custom driver which has access to the serializer (or
> making the serializer accessible to rich functions, and I think there be
> dragons).
> If the idea of a self-join is agreeable, I'd like to work out a rough
> implementation and go from there.
> [0] https://en.wikipedia.org/wiki/Join_%28SQL%29#Self-join
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