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https://issues.apache.org/jira/browse/TAJO-853?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14028209#comment-14028209
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ASF GitHub Bot commented on TAJO-853:
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Github user hyunsik commented on the pull request:
https://github.com/apache/tajo/pull/28#issuecomment-45783447
Thank you for your contribution. I'm reviewing this patch. Is it ready to
be committed or is it still working?
> Refactoring FilterPushDown for OUTER JOIN
> -----------------------------------------
>
> Key: TAJO-853
> URL: https://issues.apache.org/jira/browse/TAJO-853
> Project: Tajo
> Issue Type: Improvement
> Reporter: Hyoungjun Kim
> Assignee: Hyoungjun Kim
> Priority: Minor
>
> Currently Tajo doesn't support a filter OUTER JOIN's ON clause.
> or has some bugs. There is some rules for this in the following urls.
> -
> http://www.ibm.com/developerworks/data/library/techarticle/purcell/0112purcell.html
> - https://cwiki.apache.org/confluence/display/Hive/OuterJoinBehavior
> Briefly summarized as follows.
> - Join Predicate on Preserved Row Table: Used for join condition(not filter)
> - Join Predicate on Null Supplying Table: Can push down to the table scan
> - Where Predicate on Preserved Row Table: Can push down to the table scan
> - Where Predicate on Null Supplying Table: Used for filter with join result
> data. This filter condition is attached to SELECTION Node.
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