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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-1437) [Optimization] Rewrite GroupBy-Foreach-flatten(group) to Distinct
Date Fri, 04 Jun 2010 05:03:27 GMT

     [ https://issues.apache.org/jira/browse/PIG-1437?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ashutosh Chauhan updated PIG-1437:
----------------------------------

    Release Note:   (was: 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. )
     Description: 
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. 

> [Optimization] Rewrite GroupBy-Foreach-flatten(group) to Distinct
> -----------------------------------------------------------------
>
>                 Key: PIG-1437
>                 URL: https://issues.apache.org/jira/browse/PIG-1437
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Ashutosh Chauhan
>            Priority: Minor
>
> 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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