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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-3784) de-emphasize mapjoin hint
Date Fri, 25 Jan 2013 13:29:16 GMT

     [ https://issues.apache.org/jira/browse/HIVE-3784?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Namit Jain updated HIVE-3784:
-----------------------------

    Attachment: hive.3784.16.patch
    
> de-emphasize mapjoin hint
> -------------------------
>
>                 Key: HIVE-3784
>                 URL: https://issues.apache.org/jira/browse/HIVE-3784
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: hive.3784.10.patch, hive.3784.11.patch, hive.3784.12.patch, hive.3784.13.patch,
hive.3784.14.patch, hive.3784.15.patch, hive.3784.16.patch, hive.3784.1.patch, hive.3784.2.patch,
hive.3784.3.patch, hive.3784.4.patch, hive.3784.5.patch, hive.3784.6.patch, hive.3784.7.patch,
hive.3784.8.patch, hive.3784.9.patch
>
>
> hive.auto.convert.join has been around for a long time, and is pretty stable.
> When mapjoin hint was created, the above parameter did not exist.
> The only reason for the user to specify a mapjoin currently is if they want
> it to be converted to a bucketed-mapjoin or a sort-merge bucketed mapjoin.
> Eventually, that should also go away, but that may take some time to stabilize.
> There are many rules in SemanticAnalyzer to handle the following trees:
> ReduceSink -> MapJoin
> Union      -> MapJoin
> MapJoin    -> MapJoin
> This should not be supported anymore. In any of the above scenarios, the
> user can get the mapjoin behavior by setting hive.auto.convert.join to true
> and not specifying the hint. This will simplify the code a lot.
> What does everyone think ?

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