[jira] [Created] (AVRO-2899) JsonEncoder writes type information for not-null union

["Werner Daehn (Jira)" <ji...@apache.org>]

Werner Daehn created AVRO-2899:
----------------------------------

             Summary: JsonEncoder writes type information for not-null union
                 Key: AVRO-2899
                 URL: https://issues.apache.org/jira/browse/AVRO-2899
             Project: Apache Avro
          Issue Type: Bug
          Components: java
    Affects Versions: 1.9.2
            Reporter: Werner Daehn


_Summary: A union of [null,string] should output the value as such when using the JsonEncoder. To accomplish that, a single line needs to be changed in the JsonEncoder.java. I don't believe there are side effects but not sure - looking for validation._

 

When the schema looks like 

{{name: "text", type: ["null",\{"type":"string"}] }}

the JsonEncoder creates a Json object explicitly stating the type. So the created json is

{{text: \{ "string": "Hello World" }}}

instead of

{{text: "Hello World"}}

I have searched for this issue and people complain frequently but no real resolution. 

While I understand why this is done, the JsonDecoder needs to know what type to add in case of a union, it does not make sense in a not-null union where there is either a string value or not.

 

I would argue, in the simple case where there is a union of two elements and the first is the NULL symbol, the extra text can be omitted. Hence I have changed the writeIndex line in the JsonEncoder from

[https://github.com/apache/avro/blob/c903aa6d6fc42d3c347f95d469a8364ea44165e8/lang/java/avro/src/main/java/org/apache/avro/io/JsonEncoder.java#L297]

{{if (symbol != Symbol.NULL) {}}

to

{{if (symbol != Symbol.NULL && (top.symbols.length > 2 || top.getSymbol(0) != Symbol.NULL)) {}}

 

It should not have a side effect on the JsonDecoder either, as in case of schema evolution - making a field null-able - this must be resolved anyhow. I am not sure about that however.

 

 



--
This message was sent by Atlassian Jira
(v8.3.4#803005)