[jira] [Created] (BEAM-3160) Type based coder inference incorrectly assumes that a coder for one type is equivalent to every other coder for that type.

[Luke Cwik (JIRA)]

Luke Cwik created BEAM-3160:
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             Summary: Type based coder inference incorrectly assumes that a 
coder for one type is equivalent to every other coder for that type.
                 Key: BEAM-3160
                 URL: https://issues.apache.org/jira/browse/BEAM-3160
             Project: Beam
          Issue Type: Bug
          Components: sdk-java-core
            Reporter: Luke Cwik
             Fix For: 2.3.0


We should prevent coder inference from assuming that two coders for the same 
type are interchangeable.

Two Avro GenericRecord coders with different schemas are considered identical 
and an arbitrary one is returned by the Coder/Type inference system if the 
GenericRecord type appears multiple times.
e.g.
*KvCoder.of(AvroCoder.of(SchemaA), AvroCoder.of(SchemaB))* after coder 
inference for the type *KV<GenericRecord, GenericRecord>* will return 
*KvCoder.of(AvroCoder.of(SchemaX), AvroCoder.of(SchemaX))* where SchemaX is 
either SchemaA or SchemaB.

Code:
https://github.com/apache/beam/blob/v2.1.1/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/CoderRegistry.java#L420
 and other Type -> Coder maps in the same file should prevent insertion if the 
type already exists.



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