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Type:
Improvement
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Status: Open
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Priority:
Minor
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Resolution: Unresolved
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Affects Version/s: None
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Fix Version/s: None
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Component/s: Core
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Labels:None
Attempting to cogroup an Avro-based table with a Writable-based table produces an exception like:
java.lang.ClassCastException: org.apache.crunch.types.writable.WritableType cannot be cast to org.apache.crunch.types.avro.AvroType at org.apache.crunch.types.avro.Avros.collections(Avros.java:409) at org.apache.crunch.types.avro.AvroTypeFamily.collections(AvroTypeFamily.java:106) at org.apache.crunch.lib.Cogroup.cogroup(Cogroup.java:63) at org.apache.crunch.lib.Cogroup.cogroup(Cogroup.java:46) at org.apache.crunch.impl.dist.collect.PTableBase.cogroup(PTableBase.java:176)
This technical limitation makes sense, and the exception message is relatively self-explanatory (at least for anyone who is familiar with Crunch concepts), so I don't think there's really a bug to be fixed. However both the documentation in the code javadoc (Cogroup class, Set#difference, and PTable#cogroup) and the user guide section about Cogroups (https://crunch.apache.org/user-guide.html#cogroups) could be updated to clarify that all tables involved in a cogroup operation must have the same type family.