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From "Pradeep Kamath (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-627) PERFORMANCE: multi-query optimization
Date Wed, 25 Mar 2009 00:45:51 GMT

    [ https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12688957#action_12688957
] 

Pradeep Kamath commented on PIG-627:
------------------------------------

+1 - committed patch by Gunther to merge changes in trunk to multiquery branch - thanks for
the contribution Gunther.

> PERFORMANCE: multi-query optimization
> -------------------------------------
>
>                 Key: PIG-627
>                 URL: https://issues.apache.org/jira/browse/PIG-627
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: 1.0.0
>            Reporter: Olga Natkovich
>         Attachments: file_cmds-0305.patch, merge_741727_HEAD__0324.patch, merge_741727_HEAD__0324_2.patch,
multi-store-0303.patch, multi-store-0304.patch, multiquery-phase2_0313.patch, multiquery-phase2_0323.patch,
multiquery_0223.patch, multiquery_0224.patch, multiquery_0306.patch, multiquery_explain_fix.patch
>
>
> Currently, if your Pig script contains multiple stores and some shared computation, Pig
will execute several independent queries. For instance:
> A = load 'data' as (a, b, c);
> B = filter A by a > 5;
> store B into 'output1';
> C = group B by b;
> store C into 'output2';
> This script will result in map-only job that generated output1 followed by a map-reduce
job that generated output2. As the resuld data is read, parsed and filetered twice which is
unnecessary and costly. 

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