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https://issues.apache.org/jira/browse/PIG-4724?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Prashant Kommireddi updated PIG-4724:
-------------------------------------
Description:
{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
was:
{code}
A = load 'data';
B = filter A by $0 == 'THIS_DOES_NOT_EXIST';
C = group A 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
> 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: 0.15.0
> Reporter: 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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