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https://issues.apache.org/jira/browse/CRUNCH-667?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Andrew Olson updated CRUNCH-667:
--------------------------------
Description:
Attempting to cogroup an Avro-based table with a Writable-based table produces
an exception like:
{noformat}
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){noformat}
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.
was:
Attempting to cogroup an Avro-based table with a Writable-based table produces
an exception like:
{noformat}
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){noformat}
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.
> Documentation should mention that cogrouping requires a common type family
> --------------------------------------------------------------------------
>
> Key: CRUNCH-667
> URL: https://issues.apache.org/jira/browse/CRUNCH-667
> Project: Crunch
> Issue Type: Improvement
> Components: Core
> Reporter: Andrew Olson
> Assignee: Josh Wills
> Priority: Minor
>
> Attempting to cogroup an Avro-based table with a Writable-based table
> produces an exception like:
> {noformat}
> 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){noformat}
> 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.
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