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From "John Sichi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-972) support views
Date Thu, 14 Jan 2010 21:51:55 GMT

    [ https://issues.apache.org/jira/browse/HIVE-972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12800376#action_12800376
] 

John Sichi commented on HIVE-972:
---------------------------------

Here's my rationale:

(1) A view is a logical object, so by default, its definition fits naturally at the logical
level (table) rather than the physical level (storage descriptor).

(2) For a view object, we need both original text and expanded text.  However, if we end up
needing it per partition later for "very smart" materialized views, we'll only need the expanded
text (the original text is only needed for user friendly DESCRIBE and for recompiling the
view).  So we would just add one new attribute on partition (not storage descriptor).

(3) Most storage descriptors (describing partitions of tables) have nothing to do with views
at all.  So adding a new attribute there is just deadweight unless we actually get to "very
smart" materialized views.

By "very smart", I mean that we'll be able to avoid rematerializing old partitions when the
view definition changes.  This is the only reason I can think of why we would ever end up
needing a view definition per partition (so that we can compare the old and new view definitions
and see if one is derivable from the other).  It seems like that is unlikely to happen very
soon.  Is there some other case where we'd need it?


> support views
> -------------
>
>                 Key: HIVE-972
>                 URL: https://issues.apache.org/jira/browse/HIVE-972
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Metastore, Query Processor
>            Reporter: Namit Jain
>            Assignee: John Sichi
>         Attachments: HIVE-972.1.patch
>
>
> Hive currently does not support views. 
> It would be a very nice feature to have.

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