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https://issues.apache.org/jira/browse/BEAM-2658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16097693#comment-16097693
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Neville Li commented on BEAM-2658:
----------------------------------
Types covered by each {{CoderProvider}} may overlap and we might want sort them
based on scope and not name.
2 ideas:
1. Add a `List<TypeDescriptor> getSupportedTypes()` and make sure that when 2
providers overlap, the one with the narrower supported types gets precedence.
Won't work with `DefaultCoder` though. Also a class can implement multiple
interfaces and it doesn't specify which one has higher precedence. For example
`ProtoCoder` supports `Message.class` while `SerializableCoder` supports
`Serializable.class` but generated Protobuf classes also implements
`Serializable`.
2. Assign an arbitrary int precedent to each coder, similar to UNIX rc/motd
files, and store registered coders in a `TreeMap<Integer,
List<CoderProvider>>`. Not elegant but works.
> SerializableCoder has higher precedence over ProtoCoder in
> CoderRegistry#getCoder
> ---------------------------------------------------------------------------------
>
> Key: BEAM-2658
> URL: https://issues.apache.org/jira/browse/BEAM-2658
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Affects Versions: 2.0.0
> Reporter: Neville Li
> Assignee: Davor Bonaci
> Priority: Minor
>
> {code}
> import com.google.protobuf.Timestamp;
> import org.apache.beam.sdk.Pipeline;
> import org.apache.beam.sdk.coders.CannotProvideCoderException;
> import org.apache.beam.sdk.coders.Coder;
> import org.apache.beam.sdk.options.PipelineOptions;
> import org.apache.beam.sdk.options.PipelineOptionsFactory;
> public class CoderTest {
> public static void main(String[] args) throws CannotProvideCoderException {
> PipelineOptions options = PipelineOptionsFactory.fromArgs(args).create();
> Pipeline pipeline = Pipeline.create(options);
> Coder<Timestamp> coder =
> pipeline.getCoderRegistry().getCoder(Timestamp.class);
> // class org.apache.beam.sdk.coders.SerializableCoder
> System.out.println(coder.getClass());
> }
> }
> {code}
> Right now we're sorting {{CoderProviderRegistrar}}s by canonical name but
> {{SerializableCoderProvider}} should be added last as a fallback if there're
> other {{CoderProvider}}s that support the same type.
> {code}
> Set<CoderProviderRegistrar> registrars =
> Sets.newTreeSet(ObjectsClassComparator.INSTANCE);
> {code}
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