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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (AVRO-891) Change SpecificDatumReader to default reader schema from loaded class
Date Thu, 22 Sep 2011 19:09:26 GMT

     [ https://issues.apache.org/jira/browse/AVRO-891?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Doug Cutting updated AVRO-891:
------------------------------

    Summary: Change SpecificDatumReader to default reader schema from loaded class  (was:
Change SpecificDatum)

> Change SpecificDatumReader to default reader schema from loaded class
> ---------------------------------------------------------------------
>
>                 Key: AVRO-891
>                 URL: https://issues.apache.org/jira/browse/AVRO-891
>             Project: Avro
>          Issue Type: Improvement
>          Components: java
>    Affects Versions: 1.5.4
>         Environment: OSX 10.7
>            Reporter: Alex Holmes
>            Assignee: Doug Cutting
>             Fix For: 1.6.0
>
>         Attachments: AVRO-891.patch, AVRO-891.patch
>
>
> An AvroRuntimeException exception is thrown when attempting to read an Avro file serialized
with an older version of a schema containing a field which has been subsequently removed in
the newer schema.
> *Exception*
> {code}
> Exception in thread "main" org.apache.avro.AvroRuntimeException: Bad index
> 	at Record.put(Unknown Source)
> 	at org.apache.avro.generic.GenericData.setField(GenericData.java:463)
> 	at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:166)
> 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:138)
> 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:129)
> 	at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233)
> 	at org.apache.avro.file.DataFileStream.next(DataFileStream.java:220)
> 	at Read.readFromAvro(Unknown Source)
> 	at Read.main(Unknown Source)
> {code}
> *Steps to reproduce*
> #  Generate code for schema v1 and v2
> #  Write an Avro file with the v1 code-generated Record class using the DataFileWriter
and SpecificDatumWriter
> #  (informational only) Read the Avro file using the v1 code-generated Record class using
DataFileStream and SpecificDatumReader (output follows)
> {code}
> Record@2ec791b9[name=r1,id=1]
> Record@bd86fd3[name=r2,id=2]
> {code}
> #  Read the Avro file using the v2 code-generated Record class using DataFileStream and
SpecificDatumReader
> *Schema details*
> v1 schema:
> {code}
> {"name": "Record", "type": "record",
>   "fields": [
>     {"name": "name", "type": "string"},
>     {"name": "id", "type": "int"}
>   ]
> }
> {code}
> v2 schema:
> {code}
> {"name": "Record", "type": "record",
>   "fields": [
>     {"name": "name", "type": "string"}
>   ]
> }
> {code}
> *Write code*
> {code}
>   public static Record createRecord(String name, int id) {
>     Record record = new Record();
>     record.name = name;
>     record.id = id;
>     return record;
>   }
>   public static void writeToAvro(OutputStream outputStream)
>       throws IOException {
>     DataFileWriter<Record> writer =
>         new DataFileWriter<Record>(new SpecificDatumWriter<Record>());
>     writer.create(Record.SCHEMA$, outputStream);
>     writer.append(createRecord("r1", 1));
>     writer.append(createRecord("r2", 2));
>     writer.close();
>     outputStream.close();
>   }
> {code}
> *Read code*
> {code}
>   public static void readFromAvro(InputStream is) throws IOException {
>     DataFileStream<Record> reader = new DataFileStream<Record>(
>             is, new SpecificDatumReader<Record>());
>     for (Record a : reader) {
>       System.out.println(ToStringBuilder.reflectionToString(a));
>     }
>     IOUtils.cleanup(null, is);
>     IOUtils.cleanup(null, reader);
>   }
> {code}

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