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From "Aviem Zur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (BEAM-1987) extend join-library to support 3+ PCollections
Date Tue, 18 Apr 2017 05:00:47 GMT

    [ https://issues.apache.org/jira/browse/BEAM-1987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15972128#comment-15972128
] 

Aviem Zur commented on BEAM-1987:
---------------------------------

Sounds like a good feature.

AFAIK the semantics of joins in relational algebra discuss 2 operands[1].
We need to be clear on the semantics of the operations we are adding and have good documentation
for them.

[1] https://en.wikipedia.org/wiki/Relational_algebra#Outer_joins

> extend join-library to support 3+ PCollections
> ----------------------------------------------
>
>                 Key: BEAM-1987
>                 URL: https://issues.apache.org/jira/browse/BEAM-1987
>             Project: Beam
>          Issue Type: Improvement
>          Components: sdk-java-extensions
>            Reporter: Xu Mingmin
>            Assignee: Xu Mingmin
>
> {{join.class}} in join-library can handle two source PCollections, to perform inner/left_outer/right_outer
join. 
> Extend the capability to handle more upstream PCollections.



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