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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-792) PERFORMANCE: Support skewed join in pig
Date Mon, 27 Jul 2009 17:32:14 GMT

    [ https://issues.apache.org/jira/browse/PIG-792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12735674#action_12735674
] 

Alan Gates commented on PIG-792:
--------------------------------

I'll take a look at the revised patch today.

> PERFORMANCE: Support skewed join in pig
> ---------------------------------------
>
>                 Key: PIG-792
>                 URL: https://issues.apache.org/jira/browse/PIG-792
>             Project: Pig
>          Issue Type: Improvement
>            Reporter: Sriranjan Manjunath
>         Attachments: skewedjoin.patch
>
>
> Fragmented replicated join has a few limitations:
>  - One of the tables needs to be loaded into memory
>  - Join is limited to two tables
> Skewed join partitions the table and joins the records in the reduce phase. It computes
a histogram of the key space to account for skewing in the input records. Further, it adjusts
the number of reducers depending on the key distribution.
> We need to implement the skewed join in pig.

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