[jira] [Commented] (HIVE-784) Support uncorrelated subqueries in the WHERE clause

["Harish Butani (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13784810#comment-13784810 ] 

Harish Butani commented on HIVE-784:
------------------------------------

Uploaded a Spec and preliminary patch.
Has support for:
- In/Not In: non-correlated and correlated
- Exists/Not Exists

The approach is to do Algebraic transformations during genPlan.

The patch doesn't have all the checks from the document. For e.g. check to disallow nested SubQueries is missing.
Will add these and more egs in the next patch.


> Support uncorrelated subqueries in the WHERE clause
> ---------------------------------------------------
>
>                 Key: HIVE-784
>                 URL: https://issues.apache.org/jira/browse/HIVE-784
>             Project: Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Ning Zhang
>            Assignee: Matthew Weaver
>         Attachments: HIVE-784.1.patch.txt, HIVE-784.2.patch, SubQuerySpec.pdf
>
>
> Hive currently only support views in the FROM-clause, some Facebook use cases suggest that Hive should support subqueries such as those connected by IN/EXISTS in the WHERE-clause. 



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