[jira] Commented: (PIG-627) PERFORMANCE: multi-query optimization

["Alan Gates (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12672464#action_12672464 ] 

Alan Gates commented on PIG-627:
--------------------------------

See http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification for a more concrete proposal that incorporates and extends the thoughts in the last comment.

> 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
>
>
> 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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