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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1180) Support Common Table Expressions (CTEs) in Hive
Date Thu, 18 Feb 2010 22:47:28 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835456#action_12835456
] 

Ning Zhang commented on HIVE-1180:
----------------------------------

It seems that he benefits of CTE are 1) its support of recursion and 2) query-level temp table
materialization (if the optimizer chooses so). 

I think (2) is a good addition to Hive, given that we have views now and need to add the support
of session-level temp tables.

(1) is a major extension and it may be unsafe -- the query may never terminate (well UDFs
are undeciable, but HiveQL itself is currently). I was wondering how many customers really
need recursions given that we have UDF support.

> Support Common Table Expressions (CTEs) in Hive
> -----------------------------------------------
>
>                 Key: HIVE-1180
>                 URL: https://issues.apache.org/jira/browse/HIVE-1180
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Jeff Hammerbacher
>
> I've seen some presentations from the PostgreSQL recently expounding the utility of CTEs
(http://en.wikipedia.org/wiki/Common_table_expressions). Should we try to support these in
Hive? I've never used them in practice, so curious to hear if the community would find them
useful.

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