[
https://issues.apache.org/jira/browse/HIVE-7159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14034466#comment-14034466
]
Harish Butani commented on HIVE-7159:
-------------------------------------
The issue with join pushdown is that now genNotNullFilterForJoinSourcePlan is
always working of the top QBJoinTree; in the original patch the joinTree was
passed in, somewhere along the line this got refactored, looking into reverting.
> For inner joins push a 'is not null predicate' to the join sources for every
> non nullSafe join condition
> --------------------------------------------------------------------------------------------------------
>
> Key: HIVE-7159
> URL: https://issues.apache.org/jira/browse/HIVE-7159
> Project: Hive
> Issue Type: Bug
> Reporter: Harish Butani
> Assignee: Harish Butani
> Attachments: HIVE-7159.1.patch, HIVE-7159.2.patch, HIVE-7159.3.patch,
> HIVE-7159.4.patch, HIVE-7159.5.patch, HIVE-7159.6.patch, HIVE-7159.7.patch
>
>
> A join B on A.x = B.y
> can be transformed to
> (A where x is not null) join (B where y is not null) on A.x = B.y
> Apart from avoiding shuffling null keyed rows it also avoids issues with
> reduce-side skew when there are a lot of null values in the data.
> Thanks to [~gopalv] for the analysis and coming up with the solution.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
