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https://issues.apache.org/jira/browse/PIG-1437?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Dai updated PIG-1437:
----------------------------
Assignee: Xuefu Zhang
Fix Version/s: 0.9.0
> [Optimization] Rewrite GroupBy-Foreach-flatten(group) to Distinct
> -----------------------------------------------------------------
>
> Key: PIG-1437
> URL: https://issues.apache.org/jira/browse/PIG-1437
> Project: Pig
> Issue Type: Sub-task
> Components: impl
> Affects Versions: 0.7.0
> Reporter: Ashutosh Chauhan
> Assignee: Xuefu Zhang
> Priority: Minor
> Fix For: 0.9.0
>
>
> Its possible to rewrite queries like this
> {code}
> A = load 'data' as (name,age);
> B = group A by (name,age);
> C = foreach B generate group.name, group.age;
> dump C;
> {code}
> or
> {code}
> (name,age);
> B = group A by (name
> A = load 'data' as,age);
> C = foreach B generate flatten(group);
> dump C;
> {code}
> to
> {code}
> A = load 'data' as (name,age);
> B = distinct A;
> dump B;
> {code}
> This could only be done if no columns within the bags are referenced
> subsequently in the script. Since in Pig-Hadoop world DISTINCT will be
> executed more effeciently then group-by this will be a huge win.
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