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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12688957#action_12688957
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Pradeep Kamath commented on PIG-627:
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+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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