[jira] [Comment Edited] (AVRO-3182) Avro in Java cannot parse the union schema from C#

["Ryan Skraba (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-3182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17398119#comment-17398119 ] 

Ryan Skraba edited comment on AVRO-3182 at 8/12/21, 3:05 PM:
-------------------------------------------------------------

Hello! It looks like this would be a change to the [specification|https://avro.apache.org/docs/1.10.2/spec.html#schemas] – it currently says that the form \{ "type" : "typeName" } should have a string name.

As a consequence, for example, we currently can't set properties on a UNION.  That's always seemed a bit odd to me, but it's never actually been a problem in practice.

I checked the python SDK and it has the same behaviour as the Java SDK:
{code:java}
avro.schema.parse('{"type": ["null", "string"]}') {code}
raises:
{code:java}
avro.schema.SchemaParseException: Undefined type: ['null', 'string'] {code}
Do you think it would be better to fix this as a bug in the C# SDK?


was (Author: ryanskraba):
Hello! It looks like this would be a change to the [specification|https://avro.apache.org/docs/1.10.2/spec.html#schemas] – it currently says that the form {{{ "type" : "typeName" } }}should have a name.

As a consequence, for example, we currently can't set properties on a UNION.  That's always seemed a bit odd to me, but it's never actually been a problem in practice.

I checked the python SDK and it has the same behaviour as the Java SDK:
{code:java}
avro.schema.parse('{"type": ["null", "string"]}') {code}
raises:
{code:java}
avro.schema.SchemaParseException: Undefined type: ['null', 'string'] {code}
Do you think it would be better to fix this as a bug in the C# SDK?

> Avro in Java cannot parse the union schema from C#
> --------------------------------------------------
>
>                 Key: AVRO-3182
>                 URL: https://issues.apache.org/jira/browse/AVRO-3182
>             Project: Apache Avro
>          Issue Type: Bug
>          Components: csharp, java
>    Affects Versions: 1.10.2
>            Reporter: Shawn Wu
>            Priority: Critical
>
> Version: 1.10.2
>  
> I need to transfer data from C# to Java.
> When I use Avro in C#, I found [Schema.ToString() in C#|https://github.com/apache/avro/blob/master/lang/csharp/src/apache/main/Schema/Schema.cs#L272] for union schema will add an extra *type* property in JSON string.
> However, the correct union schema is a JSON array.
> This is my test code in C#:
> {code:java}
> var columnCountSchema = Schema.Parse("{\"type\":\"record\",\"name\":\"columnCount\",\"namespace\":\"avro.test.header\",\"fields\":[{\"name\":\"columnCount\",\"type\":\"int\"}]}");
> var errorMessageSchema = Schema.Parse("{\"type\":\"record\",\"name\":\"errorMessage\",\"namespace\":\"avro.test.header\",\"fields\":[{\"name\":\"errorMessage\",\"type\":[\"string\",\"null\"]}]}");
> var schema = Schema.Parse($"[{columnCountSchema},{errorMessageSchema}]");
> Console.WriteLine(schema.ToString());{code}
> The output:
> {code:java}
> {"type":[{"type":"record","name":"columnCount","namespace":"avro.test.header","fields":[{"name":"columnCount","type":"int"}]},{"type":"record","name":"errorMessage","namespace":"avro.test.header","fields":[{"name":"errorMessage","type":["string","null"]}]}]}
> {code}
>  
> When I use Avro in C# to parse this union schema JSON string, it is correct. [Schema.ParseJson() in C#|https://github.com/apache/avro/blob/master/lang/csharp/src/apache/main/Schema/Schema.cs#L203]
> But when I use Avro in Java to parse the union schema in Stream from C#, there is the following error message:
> {code:java}
> org.apache.avro.SchemaParseException: No type: {"type":[{"type":"record","name":"columnCount","namespace":"avro.test.header","fields":[{"name":"columnCount","type":"int"}]},{"type":"record","name":"errorMessage","namespace":"avro.test.header","fields":[{"name":"errorMessage","type":["string","null"]}]}]}org.apache.avro.SchemaParseException: No type: {"type":[{"type":"record","name":"columnCount","namespace":"avro.test.header","fields":[{"name":"columnCount","type":"int"}]},{"type":"record","name":"errorMessage","namespace":"avro.test.header","fields":[{"name":"errorMessage","type":["string","null"]}]}]} at org.apache.avro.Schema.getRequiredText(Schema.java:1784) at org.apache.avro.Schema.parse(Schema.java:1637) at org.apache.avro.Schema$Parser.parse(Schema.java:1425) at org.apache.avro.Schema$Parser.parse(Schema.java:1413) at org.apache.avro.file.DataFileStream.initialize(DataFileStream.java:130) at org.apache.avro.file.DataFileStream.<init>(DataFileStream.java:90) at avro.AvroService.read(AvroService.java:68) at avro.AvroService$1.onResponse(AvroService.java:144) at okhttp3.internal.connection.RealCall$AsyncCall.run(RealCall.kt:519) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)
> {code}
> I think this format of union schema should be supported in Java.
>  



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