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From "Edward Capriolo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1180) Support Common Table Expressions (CTEs) in Hive
Date Thu, 18 Feb 2010 23:11:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835466#action_12835466
] 

Edward Capriolo commented on HIVE-1180:
---------------------------------------

(2) is a good addition to Hive, given that we have views now and need to add the support of
session-level temp tables.
Question, how are we going to support session level temp tables Files/tables in HDFS are going
to be tied into SessionState or a session ID in someway?

(1) From my experience map/reduce does not lend itself well to recursive work. Currently if
each recursion was a map/reduce job that would be a major strain on hadoop. (JobHistory would
have explosive growth from a few queries) Maybe there is a simple way around this.

However it is possible/practical recursive processing does open up interesting queries on
self joined tables.
id name parent
{noformat}
1 adam null
2 caan 1
3 able 1
{noformat}

Select "ALL DESCENDANTS OF ADAM"

> 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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