List<Fields> fullGroupFields = new ArrayList<Fields>();
for(int i=0; i<groupedStreams.size(); i++) {
GroupedStream gs = groupedStreams.get(i);
Fields groupFields = gs.getGroupFields();
fullGroupFields.add(groupFields);
streams.add(gs.toStream().partitionBy(groupFields));
fullInputFields.add(TridentUtils.fieldsUnion(groupFields, inputFields.get(i)));
}
return multiReduce(fullInputFields, streams, new GroupedMultiReducerExecutor(function, fullGroupFields, inputFields), outputFields);
}