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Date: Mon, 29 Oct 2012 16:28:12 +0000 (UTC)
From: "Sambavi Muthukrishnan (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
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Subject: [jira] [Commented] (HIVE-3610) Add a command "Explain dependency
 ..."
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    [ https://issues.apache.org/jira/browse/HIVE-3610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486123#comment-13486123 ] 

Sambavi Muthukrishnan commented on HIVE-3610:
---------------------------------------------

Namit: the set of inputs should be  available through hooks. But this seems like a generically useful feature - to be able to determine the dependencies for a given query, which are the sets of inputs that are processed, hence decided to make it a command that is available in HIVE.
                
> Add a command "Explain dependency ..."
> --------------------------------------
>
>                 Key: HIVE-3610
>                 URL: https://issues.apache.org/jira/browse/HIVE-3610
>             Project: Hive
>          Issue Type: New Feature
>          Components: Query Processor
>    Affects Versions: 0.9.0
>            Reporter: Sambavi Muthukrishnan
>            Assignee: Sambavi Muthukrishnan
>            Priority: Minor
>         Attachments: explain_dependency.1.patch, explain_dependency.2.patch
>
>
> Add a new command "EXPLAIN DEPENDENCY".
> Any query can be passed to EXPLAIN DEPENDENCY as with EXPLAIN (FORMATTED/EXTENDED). The output of this command will be JSON that provides the list of tables and partitions that the query depends on.
> One possible use case is to determine the set of tables/views that are used by a view, and the set of partitions that are used by a given query on that view. This will allow a view to be replicated from one Hive instance to another, since we can determine the set of objects that need to be replicated for replication of the view to be successful.
> Example output:
> {"input_tables":[{"tablename": "default@test_sambavi_v2", "tabletype": "EXTERNAL_TABLE"}, {"tablename": "default@test_sambavi_v1", "tabletype": "TABLE"}], "input partitions":["default@srcpart@ds=2008-04-08/hr=11","default@srcpart@ds=2008-04-08/hr=12"]}

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