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From "Jim Pivarski (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1548) Cannot read aliased instance in union
Date Wed, 23 Jul 2014 15:10:38 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14071839#comment-14071839
] 

Jim Pivarski commented on AVRO-1548:
------------------------------------

Since it will just be a few days, I'll wait for 1.7.7 to come out and then test my example
with the "." prefix notation.  Thanks!

> Cannot read aliased instance in union
> -------------------------------------
>
>                 Key: AVRO-1548
>                 URL: https://issues.apache.org/jira/browse/AVRO-1548
>             Project: Avro
>          Issue Type: Bug
>          Components: java
>    Affects Versions: 1.7.6
>            Reporter: Jim Pivarski
>              Labels: alias, uniontype
>
> I created an Avro file using unqualified record names (no namespace) and I want to read
them back into another JVM with qualified names.  In the second JVM, I supply a schema with
the qualified names and an alias to accept the unqualified name.  This works as expected if
the record is not part of a union, but it fails with an exception if it is part of a union.
> Here is an example that reproduces the bug.  In a Scala REPL with avro-1.7.6.jar on the
classpath,
> {code}
> import org.apache.avro.file.DataFileWriter
> import org.apache.avro.generic.GenericData
> import org.apache.avro.generic.GenericDatumWriter
> import org.apache.avro.Schema
> val parser = new Schema.Parser
> val schema = parser.parse("""{"type": "record", "name": "Unqualified1", "fields": [{"name":
"x", "type": ["null", {"type": "record", "name": "Unqualified2", "fields": [{"name": "y",
"type": "string"}]}]}]}}""")
> val unqualified2schema = schema.getField("x").schema.getTypes.get(1)
> val unqualified2instance = new GenericData.Record(unqualified2schema)
> unqualified2instance.put("y", "hello")
> val unqualified1instance = new GenericData.Record(schema)
> unqualified1instance.put("x", unqualified2instance)
> val datumWriter = new GenericDatumWriter[GenericData.Record](schema)
> val dataFileWriter = new DataFileWriter[GenericData.Record](datumWriter)
> dataFileWriter.create(schema, new java.io.File("tmp.avro"))
> dataFileWriter.append(unqualified1instance)
> dataFileWriter.close()
> {code}
> creates a file that looks like this:
> {code}
> hexdump -C tmp.avro
> 00000000  4f 62 6a 01 02 16 61 76  72 6f 2e 73 63 68 65 6d  |Obj...avro.schem|
> 00000010  61 be 02 7b 22 74 79 70  65 22 3a 22 72 65 63 6f  |a..{"type":"reco|
> 00000020  72 64 22 2c 22 6e 61 6d  65 22 3a 22 55 6e 71 75  |rd","name":"Unqu|
> 00000030  61 6c 69 66 69 65 64 31  22 2c 22 66 69 65 6c 64  |alified1","field|
> 00000040  73 22 3a 5b 7b 22 6e 61  6d 65 22 3a 22 78 22 2c  |s":[{"name":"x",|
> 00000050  22 74 79 70 65 22 3a 5b  22 6e 75 6c 6c 22 2c 7b  |"type":["null",{|
> 00000060  22 74 79 70 65 22 3a 22  72 65 63 6f 72 64 22 2c  |"type":"record",|
> 00000070  22 6e 61 6d 65 22 3a 22  55 6e 71 75 61 6c 69 66  |"name":"Unqualif|
> 00000080  69 65 64 32 22 2c 22 66  69 65 6c 64 73 22 3a 5b  |ied2","fields":[|
> 00000090  7b 22 6e 61 6d 65 22 3a  22 79 22 2c 22 74 79 70  |{"name":"y","typ|
> 000000a0  65 22 3a 22 73 74 72 69  6e 67 22 7d 5d 7d 5d 7d  |e":"string"}]}]}|
> 000000b0  5d 7d 00 3d 57 38 9b 8c  5a 9a 86 3d b8 18 60 63  |]}.=W8..Z..=..`c|
> 000000c0  5c bb c5 02 0e 02 0a 68  65 6c 6c 6f 3d 57 38 9b  |\......hello=W8.|
> 000000d0  8c 5a 9a 86 3d b8 18 60  63 5c bb c5              |.Z..=..`c\..|
> 000000dc
> {code}
> Now in a new JVM, I try to load it like this:
> {code}
> import org.apache.avro.file.DataFileReader
> import org.apache.avro.generic.GenericData
> import org.apache.avro.generic.GenericDatumReader
> import org.apache.avro.Schema
> val parser = new Schema.Parser
> val schema = parser.parse("""{"type": "record", "namespace": "com.mycompany", "name":
"Qualified1", "aliases": ["Unqualified1"], "fields": [{"name": "x", "type": ["null", {"type":
"record", "namespace": "com.mycompany", "name": "Qualified2", "aliases": ["Unqualified2"],
"fields": [{"name": "y", "type": "string"}]}]}]}}""")
> val datumReader = new GenericDatumReader[GenericData.Record](schema)
> val dataFileReader = new DataFileReader[GenericData.Record](new java.io.File("tmp.avro"),
datumReader)
> println(dataFileReader.hasNext)   // true
> println(dataFileReader.next())
> {code}
> and get the following exception:
> {code}
> org.apache.avro.AvroTypeException: Found Unqualified2, expecting union
>         at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:231)
>         at org.apache.avro.io.parsing.Parser.advance(Parser.java:88)
>         at org.apache.avro.io.ResolvingDecoder.readIndex(ResolvingDecoder.java:206)
>         at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:155)
>         at org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
>         at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
>         at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:151)
>         at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:142)
>         at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233)
>         at org.apache.avro.file.DataFileStream.next(DataFileStream.java:220)
>         at .<init>(<console>:17)
>         at .<clinit>(<console>)
>         at .<init>(<console>:7)
>         at .<clinit>(<console>)
>         at $print(<console>)
>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:606)
>         at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:734)
>         at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:983)
>         at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:573)
>         at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:604)
>         at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:568)
>         at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:756)
>         at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:801)
>         at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:713)
>         at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:577)
>         at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:584)
>         at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:587)
>         at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:878)
>         at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:833)
>         at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:833)
>         at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
>         at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:833)
>         at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:83)
>         at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
>         at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
>         at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
> {code}
> If I do exactly the same thing without a union type, I can read back the original record.
 Even though this example uses GenericData for simplicity, I first observed the bug using
SpecificData.
> (Motivation: I created unqualified record names in one process and then wanted to read
it back in another, where I had auto-generated specific classes.  I couldn't pollute the parent
namespace with the auto-generated classes, and that's why I qualified their names.  The union
is because sometimes the inner record is legitimately null.)



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