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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1783) CommonJoinOperator optimize the case of 1:1 join
Date Thu, 18 Nov 2010 18:46:14 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1783?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933516#action_12933516
] 

Namit Jain commented on HIVE-1783:
----------------------------------

+1

running tests

> CommonJoinOperator optimize the case of 1:1 join
> ------------------------------------------------
>
>                 Key: HIVE-1783
>                 URL: https://issues.apache.org/jira/browse/HIVE-1783
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Siying Dong
>            Assignee: Siying Dong
>            Priority: Minor
>         Attachments: HIVE-1783.1.patch, HIVE-1783.2.patch, HIVE-1783.3.patch, HIVE-1783.4.patch
>
>
> CommonJoinOperator.genObject() is expensive. It does a recursive and keeps lots of states
because it has to:
> 1. handle null cases for outer joins
> 2. handle the case of duplicated keys from one join party
> We can do a minor optimization to detect a 1:1 join (which is quite common) before calling
CommonJoinOperator.genObject() and forward columns in a simple for-loop if we are sure neither
of 1 or 2 will happen.

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