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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-741) Add LIMIT as a statement that works in nested FOREACH
Date Thu, 30 Apr 2009 01:12:30 GMT

     [ https://issues.apache.org/jira/browse/PIG-741?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alan Gates updated PIG-741:
---------------------------

    Attachment: PIG-741.patch

> Add LIMIT as a statement that works in nested FOREACH
> -----------------------------------------------------
>
>                 Key: PIG-741
>                 URL: https://issues.apache.org/jira/browse/PIG-741
>             Project: Pig
>          Issue Type: New Feature
>            Reporter: David Ciemiewicz
>            Assignee: Alan Gates
>             Fix For: 0.3.0
>
>         Attachments: PIG-741.patch
>
>
> I'd like to compute the top 10 results in each group.
> The natural way to express this in Pig would be:
> {code}
> A = load '...' using PigStorage() as (
>     date: int,
>     count: int,
>     url: chararray
> );
> B = group A by ( date );
> C = foreach B {
>     D = order A by count desc;
>     E = limit D 10;
>     generate
>         FLATTEN(E);
>     };
> dump C;
> {code}
> Yeah, I could write a UDF / PiggyBank function to take the top n results. But since LIMIT
already exists as a statement, it seems like it should also work in the nested foreach context.
> Example workaround code.
> {code}
> C = foreach B {
>     D = order A by count desc;
>     E = util.TOP(D, 10);
>     generate
>         FLATTEN(E);
>     };
> dump C;
> {code}

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