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From "Pradeep Kamath (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-627) PERFORMANCE: multi-query optimization
Date Mon, 23 Mar 2009 23:39:50 GMT

    [ https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12688461#action_12688461
] 

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

+1 on Richard's patch -  multiquery-phase2_0323.patch, patch committed to multiquery branch
- thanks for the contribution Richard.

A general comment for the multiquery work is to introduce some negative test cases (which
return POStatus.STATUS_ERR from some operator in the map or reduce plan affected by the multiQuqeryOptimizer)
 at some point.

> 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, 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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