Details
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Bug
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Status: Triage Needed
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P1
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Resolution: Fixed
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None
Description
This, according to "4.2.2.1 GroupByKey and unbounded PCollections" in https://beam.apache.org/documentation/programming-guide/.
If you do apply GroupByKey or CoGroupByKey to a group of unbounded PCollections without setting either a non-global windowing strategy, a trigger strategy, or both for each collection, Beam generates an IllegalStateException error at pipeline construction time.
Example where this doesn't happen in Python SDK: https://stackoverflow.com/questions/60623246/merge-pcollection-with-apache-beam
I also believe that this unit test should fail, since test_stream is unbounded, uses global window, and has no triggers.
def test_global_window_gbk_fail(self): with TestPipeline() as p: test_stream = TestStream() _ = p | test_stream | GroupByKey()