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https://issues.apache.org/jira/browse/CALCITE-2968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16806610#comment-16806610
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Stamatis Zampetakis commented on CALCITE-2968:
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There has been a discussion on this subject in the dev list. See thread [Join,
SemiJoin,
Correlate|https://mail-archives.apache.org/mod_mbox/calcite-dev/201903.mbox/%3C8EEA04A0-4A77-4283-BD20-B019E19AE126%40apache.org%3E]
which seems to have reached consensus. I think the discussion there supersedes
the current proposal so I would prefer to go towards that direction.
> New AntiJoin relational expression
> ----------------------------------
>
> Key: CALCITE-2968
> URL: https://issues.apache.org/jira/browse/CALCITE-2968
> Project: Calcite
> Issue Type: New Feature
> Reporter: Ruben Quesada Lopez
> Priority: Major
>
> The goal of this ticket is to follow the discussion started in CALCITE-2920
> (and its [PR|https://github.com/apache/calcite/pull/1110]).
> With the implementation of CALCITE-2920, RelBuilder has now a method to
> create an AntiJoin. However, since, for the moment, there is no "AntiJoin"
> expression, the only possibility to build an AntiJoin is using a
> LogicalCorrelate with SemiJoinType.ANTI, and that's exactly what this method
> does, for now.
> The idea would be to "generalize" this with the creation of a new AntiJoin
> (a.k.a. AntiSemiJoin) relational expression.
> Some ideas about how to implement it:
> - Modify SemiJoin class: add a new instance field protected final
> SemiJoinType semiJoinType;, which will be by default SemiJoinType.SEMI (to
> ensure backwards compatibility); but that could also be SemiJoinType.ANTI, to
> represent an AntiJoin (a.k.a. AntiSemiJoin)
> - We could easily have two implementations of Antijoin:
> -- a) Enumerable: small modification in EnumerableSemiJoin and
> EnumerableSemiJoinRule in order to propagate the SemiJoinType, plus a new
> antiJoin method in EnumerableDefaults (basically the same as semiJoin method,
> but with a "not contains" predicate instead of "contains")
> -- b) Correlate: small modification in JoinToCorrelateRule to propagate the
> SemiJoin.semiJoinType will suffice to create the appropriate LogicalCorrelate
> with type SEMI / ANTI
> - RelBuilder antiJoin method would no longer create a LogicalCorrelate
> type=ANTI, but instead a SemiJoin type=ANTI (using a new method in
> SemiJoinFactory that would accept an additional SemiJoinType parameter).
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