[
https://issues.apache.org/jira/browse/PIG-1437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12875481#action_12875481
]
Ashutosh Chauhan commented on PIG-1437:
---------------------------------------
Since this is logical transformation of query plan, logical optimizer is the
ideal place for this optimization. But I think it instead might be easier to do
on MR plan after it is generated.
> [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.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
