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https://issues.apache.org/jira/browse/FLINK-685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17329581#comment-17329581
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Flink Jira Bot commented on FLINK-685:
--------------------------------------
This issue is assigned but has not received an update in 7 days so it has been
labeled "stale-assigned". If you are still working on the issue, please give an
update and remove the label. If you are no longer working on the issue, please
unassign so someone else may work on it. In 7 days the issue will be
automatically unassigned.
> Add support for semi-joins
> --------------------------
>
> Key: FLINK-685
> URL: https://issues.apache.org/jira/browse/FLINK-685
> Project: Flink
> Issue Type: New Feature
> Components: API / DataSet
> Reporter: GitHub Import
> Assignee: pietro pinoli
> Priority: Minor
> Labels: github-import, stale-assigned, stale-minor
>
> A semi-join is basically a join filter. One input is "filtering" and the
> other one is "filtered".
> A tuple of the "filtered" input is emitted exactly once if the "filtering"
> input has one (ore more) tuples with matching join keys. That means that the
> output of a semi-join has the same type as the "filtered" input and the
> "filtering" input is completely discarded.
> In order to support a semi-join, we need to add an additional physical
> execution strategy, that ensures, that a tuple of the "filtered" input is
> emitted only once if the "filtering" input has more than one tuple with
> matching keys. Furthermore, a couple of optimizations compared to standard
> joins can be done such as storing only keys and not the full tuple of the
> "filtering" input in a hash table.
> ---------------- Imported from GitHub ----------------
> Url: https://github.com/stratosphere/stratosphere/issues/685
> Created by: [fhueske|https://github.com/fhueske]
> Labels: enhancement, java api, runtime,
> Milestone: Release 0.6 (unplanned)
> Created at: Mon Apr 14 12:05:29 CEST 2014
> State: open
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