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From "LINZ, Arnaud" <AL...@bouyguestelecom.fr>
Subject Multiple keys in reduceGroup ?
Date Thu, 22 Oct 2015 10:20:48 GMT

Trying to understand why my code was giving strange results, I’ve ended up adding “useless”
controls in my code and came with what seems to me a bug. I group my dataset according to
a key, but in the reduceGroup function I am passed values with different keys.

My code has the following pattern (mix of java & pseudo-code in []) :

inputDataSet [of InputRecord]
.joinWithTiny(referencesDataSet [of Reference])
.where([InputRecord SecondaryKeySelector]).equalTo([Reference KeySelector])

.groupBy([PrimaryKeySelector : Tuple2<InputRecord, Reference> -> value.f0.getPrimaryKey()])
.sortGroup([DateKeySelector], Order.ASCENDING)
.reduceGroup(new ReduceFunction<InputRecord, OutputRecord>() {
       public void reduce(Iterable< Tuple2<InputRecord, Reference>> values,  Collector<OutputRecord>
out) throws Exception {
             // Issue : all values do not share the same key
      final List<Tuple2<InputRecord, Reference>> listValues = new ArrayList<Tuple2<InputRecord,
             for (final Tuple2<InputRecord, Reference>value : values) { listValues.add(value);

final long primkey = listValues.get(0).f0.getPrimaryKey();
       for (int i = 1; i < listValues.size(); i++) {
            if (listValues.get(i).f0.getPrimaryKey() != primkey) {
                      throw new IllegalStateException(primkey + " != " + listValues.get(i).f0.getPrimaryKey());
                    ==> This exception is fired !
}) ;

I use the current 0.10 snapshot. The issue appears in local cluster mode unit tests as well
as in yarn mode (however it’s ok when I test it with very few elements).

The sortGroup is not the cause of the problem, as I do get the same error without it.

Have I misunderstood the grouping concept or is it really an awful bug?

Best regards,


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