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https://issues.apache.org/jira/browse/CRUNCH-601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15425337#comment-15425337
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Mikael Goldmann commented on CRUNCH-601:
----------------------------------------
This (on top of the patch) passes the test even for length zero (but there may
of course be other corner cases as long as one trusts getSize() == 0).
{code}
// In crunch-core/src/main/java/org/apache/crunch/lib/Aggregate.java
public static <S> PObject<Long> length(PCollection<S> collect) {
PTypeFamily tf = collect.getTypeFamily();
PTable<Integer, Long> countTable = collect
.parallelDo("Aggregate.count", new MapFn<S, Pair<Integer, Long>>() {
public Pair<Integer, Long> map(S input) {
return Pair.of(1, 1L);
}
public void cleanup(Emitter<Pair<Integer, Long>> e) {
e.emit(Pair.of(1, 0L));
}
}, tf.tableOf(tf.ints(), tf.longs()))
.groupByKey(GroupingOptions.builder().numReducers(1).build())
.combineValues(Aggregators.SUM_LONGS());
PCollection<Long> count = countTable.values();
final FirstElementPObject<Long> first = new FirstElementPObject<>(count);
return new PObject<Long>() {
@Override
public Long getValue() {
final Long value = first.getValue();
return value == null ? 0 : value;
}
};
}
{code}
> Short PCollections in SparkPipeline get length null.
> ----------------------------------------------------
>
> Key: CRUNCH-601
> URL: https://issues.apache.org/jira/browse/CRUNCH-601
> Project: Crunch
> Issue Type: Bug
> Components: Spark
> Affects Versions: 0.13.0
> Environment: Running in local mode on Mac as well as in a ubuntu
> 14.04 docker container
> Reporter: Mikael Goldmann
> Priority: Minor
> Attachments: CRUNCH-601.patch, SmallCollectionLengthTest.java
>
>
> I'll attach a file with a test that I would expect to pass but which fails.
> It creates five PCollection<String> of lengths 0, 1, 2, 3, 4 gets the
> lengths, runs the pipeline and prints the lengths. Finally it asserts that
> all lengths are non-null.
> I would expect it to print lengths 0, 1, 2, 3, 4 and pass.
> What it does is print lengths null, null, null, 3, 4 and fail.
> I think the underlying reason is the use of getSize() on an unmaterialized
> object and assuming that when the estimate that getSize() returns is 0, then
> the PCollection is guaranteed to be empty, which is false in some cases.
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