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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-7) Optimize execution of algebraic functions
Date Fri, 30 Nov 2007 17:35:45 GMT

    [ https://issues.apache.org/jira/browse/PIG-7?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12547218

Alan Gates commented on PIG-7:


Thanks for the feedback, I'll address the first two issues.

On the third issue, I have a question.  Can you give me an example of a pig script that will
not be combinable in this case?  If I do something like:

a = load '/user/pig/tests/data/singlefile/studenttab10k';
b = group a by $0;
c = foreach b generate group, COUNT($1), SUM($1.$2);
d = filter c by $1 > '10';
dump d;

That still makes use of the combiner.

> Optimize execution of algebraic functions
> -----------------------------------------
>                 Key: PIG-7
>                 URL: https://issues.apache.org/jira/browse/PIG-7
>             Project: Pig
>          Issue Type: Improvement
>          Components: impl
>            Reporter: Olga Natkovich
>            Assignee: Alan Gates
>         Attachments: combiner.patch
> Algebraic are functions that can be computed incrementally like count(X), SUM(X), etc.
They can be computed effciently by doing the first level computation using hadoop combiner.
This can give a significant (2-3x) speedup for many aggregation queries. 
> Several users asked us for this feature so it is pretty high priority.

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