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From "Richard Ding (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (PIG-627) PERFORMANCE: multi-query optimization
Date Fri, 13 Mar 2009 21:20:50 GMT

    [ https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681897#action_12681897
] 

Richard Ding edited comment on PIG-627 at 3/13/09 2:18 PM:
-----------------------------------------------------------

 This patch completes the phase 2 development as sepecified in the document http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification:
       # Allow multiple stores in single job
       # Merge multiple plans into the split operator
       # Terminate all but one with stores

As an example, the Pig script

{code}
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';
{code}

in the introduction of this bug now results in a single map-reduce job.

This patch is for the multi query branch.




      was (Author: rding):
     This patch completes the phase 2 development as sepecified in the document http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification:
       # Allow multiple stores in single job
       # Merge multiple plans into the split operator
       # Terminate all but one with stores

This patch is for the multi query branch.



  
> 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_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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