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Posted to dev@pig.apache.org by "Alan Gates (JIRA)" <ji...@apache.org> on 2009/11/12 02:50:39 UTC
[jira] Assigned: (PIG-792) PERFORMANCE: Support skewed join in pig
[ https://issues.apache.org/jira/browse/PIG-792?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Alan Gates reassigned PIG-792:
------------------------------
Assignee: Sriranjan Manjunath
> 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
> Assignee: 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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