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https://issues.apache.org/jira/browse/HIVE-1180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13887010#comment-13887010
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Gunther Hagleitner commented on HIVE-1180:
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I think it's reasonable to do non-recursive, non-materialized CTEs in a first
step. It still gives you some of the benefits of CTEs (temporary "view" without
metastore, multiple refs to the same subquery, simpler to write queries.) It
will, however, still be more efficient in some cases to create/drop table to
avoid re-computation. We should probably document and create follow up jira
right away.
I've gone through the initial patch and it looks good so far. Some
questions/suggestions for test cases to add:
* CTAS/create table like: Should also be supported, right? Currently you
won't be able to specify that.
* Negative test: Multiple with statements in the same query
* What about multiple CTEs, can they referencing one another? If not, is
this caught?
* Insert statement: From the grammar it looks like you might be able to
specify the CTE as the target table also (negative test), otherwise we should
probably test that you can use it as a source.
* Order by, sort by: These don't really make sense in a CTE - should they be
disallowed?
* Top level union with CTE is probably worth a test.
* CTE in view definition: Should be allowed too, right? Currently I don't
think it is.
> Support Common Table Expressions (CTEs) in Hive
> -----------------------------------------------
>
> Key: HIVE-1180
> URL: https://issues.apache.org/jira/browse/HIVE-1180
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Jeff Hammerbacher
> Assignee: Harish Butani
> Attachments: HIVE-1180.1.patch
>
>
> 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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