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https://issues.apache.org/jira/browse/AVRO-3235?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17451372#comment-17451372
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Uwe Eisele commented on AVRO-3235:
----------------------------------
Hello again,
I just saw that there is already a pull request that solves this problem and
changes the check for enums from FullName to Name:
[https://github.com/apache/avro/pull/1381/files]
Regards,
Uwe
> Avro Schema Evolution with Enum – Deserialization Crashes
> ---------------------------------------------------------
>
> Key: AVRO-3235
> URL: https://issues.apache.org/jira/browse/AVRO-3235
> Project: Apache Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.10.2
> Reporter: Bertram Beyer
> Priority: Major
>
> Originally posted on Stack Overflow in June 2020
> https://stackoverflow.com/questions/62596990/avro-schema-evolution-with-enum-deserialization-crashes/
>
> I defined two versions of a record in two separate AVCS schema files. I used
> the namespace to distinguish versions *SimpleV1.avsc*
>
> {code:json}
> {
> "type" : "record",
> "name" : "Simple",
> "namespace" : "test.simple.v1",
> "fields" : [
> {
> "name" : "name",
> "type" : "string"
> },
> {
> "name" : "status",
> "type" : {
> "type" : "enum",
> "name" : "Status",
> "symbols" : [ "ON", "OFF" ]
> },
> "default" : "ON"
> }
> ]
> }
> {code}
>
> *Example JSON*
>
> {code:java}
> {"name":"A","status":"ON"}
> {code}
> Version 2 just has an additional description field with default value.
> *SimpleV2.avsc*
>
> {code:java}
> {
> "type" : "record",
> "name" : "Simple",
> "namespace" : "test.simple.v2",
> "fields" : [
> {
> "name" : "name",
> "type" : "string"
> },
> {
> "name" : "description",
> "type" : "string",
> "default" : ""
> },
> {
> "name" : "status",
> "type" : {
> "type" : "enum",
> "name" : "Status",
> "symbols" : [ "ON", "OFF" ]
> },
> "default" : "ON"
> }
> ]
> }
> {code}
> *Example JSON*
>
> {code:java}
> {"name":"B","description":"b","status":"ON"}
> {code}
> Both schemas were serialized to Java classes. In my example I was going to
> test backward compatibility. A record written by V1 shall be read by a reader
> using V2. I wanted to see that default values are inserted. This is working
> as long as I do not use enums.
>
> {code:java}
> public class EnumEvolutionExample {
> public static void main(String[] args) throws IOException {
> Schema schemaV1 = new org.apache.avro.Schema.Parser().parse(new
> File("./src/main/resources/SimpleV1.avsc"));
> //works as well
> //Schema schemaV1 = test.simple.v1.Simple.getClassSchema();
> Schema schemaV2 = new org.apache.avro.Schema.Parser().parse(new
> File("./src/main/resources/SimpleV2.avsc"));
> test.simple.v1.Simple simpleV1 = test.simple.v1.Simple.newBuilder()
> .setName("A")
> .setStatus(test.simple.v1.Status.ON)
> .build();
>
>
> SchemaPairCompatibility schemaCompatibility =
> SchemaCompatibility.checkReaderWriterCompatibility(
> schemaV2,
> schemaV1);
> //Checks that writing v1 and reading v2 schemas is compatible
> Assert.assertEquals(SchemaCompatibilityType.COMPATIBLE,
> schemaCompatibility.getType());
>
> byte[] binaryV1 = serealizeBinary(simpleV1);
>
> //Crashes with: AvroTypeException: Found test.simple.v1.Status,
> expecting test.simple.v2.Status
> test.simple.v2.Simple v2 = deSerealizeBinary(binaryV1, new
> test.simple.v2.Simple(), schemaV1);
>
> }
>
> public static byte[] serealizeBinary(SpecificRecord record) {
> DatumWriter<SpecificRecord> writer = new
> SpecificDatumWriter<>(record.getSchema());
> byte[] data = new byte[0];
> ByteArrayOutputStream stream = new ByteArrayOutputStream();
> Encoder binaryEncoder = EncoderFactory.get()
> .binaryEncoder(stream, null);
> try {
> writer.write(record, binaryEncoder);
> binaryEncoder.flush();
> data = stream.toByteArray();
> } catch (IOException e) {
> System.out.println("Serialization error " + e.getMessage());
> }
> return data;
> }
>
> public static <T extends SpecificRecord> T deSerealizeBinary(byte[] data,
> T reuse, Schema writer) {
> Decoder decoder = DecoderFactory.get().binaryDecoder(data, null);
> DatumReader<T> datumReader = new SpecificDatumReader<>(writer,
> reuse.getSchema());
> try {
> T datum = datumReader.read(null, decoder);
> return datum;
> } catch (IOException e) {
> System.out.println("Deserialization error" + e.getMessage());
> }
> return null;
> }
> }
> {code}
> The checkReaderWriterCompatibility method confirms that schemas are
> compatible. But when I deserialize I’m getting the following exception
>
> {code:java}
> Exception in thread "main" org.apache.avro.AvroTypeException: Found
> test.simple.v1.Status, expecting test.simple.v2.Status
> at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:309)
> at org.apache.avro.io.parsing.Parser.advance(Parser.java:86)
> at org.apache.avro.io.ResolvingDecoder.readEnum(ResolvingDecoder.java:260)
> at
> org.apache.avro.generic.GenericDatumReader.readEnum(GenericDatumReader.java:267)
> at
> org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:181)
> at
> org.apache.avro.specific.SpecificDatumReader.readField(SpecificDatumReader.java:136)
> at
> org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:247)
> at
> org.apache.avro.specific.SpecificDatumReader.readRecord(SpecificDatumReader.java:123)
> at
> org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:179)
> at
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:160)
> at
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:153)
> at
> test.EnumEvolutionExample.deSerealizeBinary(EnumEvolutionExample.java:70)
> at test.EnumEvolutionExample.main(EnumEvolutionExample.java:45)
> {code}
>
> I don’t understand why Avro thinks it got a v1.Status. Namespaces are not
> part of the encoding.
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