Prashant Kommireddi created PIG-4724:
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Summary: 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 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
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