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From "Prashant Kommireddi (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (PIG-4724) GROUP ALL must create an output record in case there is no input
Date Thu, 21 Apr 2016 23:40:12 GMT

     [ https://issues.apache.org/jira/browse/PIG-4724?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Prashant Kommireddi reassigned PIG-4724:
----------------------------------------

    Assignee: Prashant Kommireddi

> GROUP ALL must create an output record in case there is no input
> ----------------------------------------------------------------
>
>                 Key: PIG-4724
>                 URL: https://issues.apache.org/jira/browse/PIG-4724
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.16.0
>            Reporter: Prashant Kommireddi
>            Assignee: Prashant Kommireddi
>
> {code}
> A = load 'data';
> B = filter A by $0 == 'THIS_DOES_NOT_EXIST';
> C = group B ALL;
> D = foreach C generate group, COUNT(B);
> {code}
> Even if the filter did not output any rows, since we are grouping on ALL the expected
output should probably be (ALL, 0). The implementation generates a pseudo key “all” for
every input on map side, thus reduce side we can combine all input together. However, this
does not work for 0 input since the reduce side does not get any input. If the input is empty,
yield a pseudo “all, 0” to reduce



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