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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Richard Ding updated PIG-627:
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    Attachment: multiquery_0306.patch

This patch contains the enhanced split operator to support multi-store queries. 
It instroduces a new MROperPlan adjuster that merges single-load mapper-only 
MapReduceOper to its predecesor based on the (implicit) split boundary. The 
goal is to reduce the total number of MR jobs for a given multi-query task.

> PERFORMANCE: multi-query optimization
> -------------------------------------
>
>                 Key: PIG-627
>                 URL: https://issues.apache.org/jira/browse/PIG-627
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: types_branch
>            Reporter: Olga Natkovich
>             Fix For: types_branch
>
>         Attachments: file_cmds-0305.patch, multi-store-0303.patch, 
> multi-store-0304.patch, multiquery_0223.patch, multiquery_0224.patch, 
> multiquery_0306.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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