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https://issues.apache.org/jira/browse/AVRO-695?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sachin Goyal updated AVRO-695:
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    Attachment: avro_circular_refs_2014_06_14.zip

[~cutting], excellent suggestion.
I have made the suggested changes in the new patch:

1) If {code}ReflectData.setCircularRefIdPrefix("some-field-name"){code} is set, 
Avro converts each RECORD schema into a UNION schema such that it can either be 
a record or a string. This should make circular references readable by other 
implementations of Avro like c, c++, php, ruby etc.
(AllowNull also works with this).

2) Added some thread-safe constructs like ThreadLocal for hash-maps used in 
circular reference code.

3) Enhanced the test-case (with detailed comments) to test regular 
deserialization and circular deserialization for a circular-ref serialized Avro.

> Cycle Reference Support
> -----------------------
>
>                 Key: AVRO-695
>                 URL: https://issues.apache.org/jira/browse/AVRO-695
>             Project: Avro
>          Issue Type: New Feature
>          Components: spec
>    Affects Versions: 1.7.6
>            Reporter: Moustapha Cherri
>         Attachments: avro-1.4.1-cycle.patch.gz, avro-1.4.1-cycle.patch.gz, 
> avro_circular_references.zip, avro_circular_refs_2014_06_14.zip
>
>   Original Estimate: 672h
>  Remaining Estimate: 672h
>
> This is a proposed implementation to add cycle reference support to Avro. It 
> basically introduce a new type named Cycle. Cycles contains a string 
> representing the path to the other reference.
> For example if we have an object of type Message that have a member named 
> previous with type Message too. If we have have this hierarchy:
> message
>   previous : message2
> message2
>   previous : message2
> When serializing the cycle path for "message2.previous" will be "previous".
> The implementation depend on ANTLR to evaluate those cycle at read time to 
> resolve them. I used ANTLR 3.2. This dependency is not mandated; I just used 
> ANTLR to speed thing up. I kept in this implementation the generated code 
> from ANTLR though this should not be the case as this should be generated 
> during the build. I only updated the Java code.
> I did not make full unit testing but you can find "avrotest.Main" class that 
> can be used a preliminary test.
> Please do not hesitate to contact me for further clarification if this seems 
> interresting.
> Best regards,
> Moustapha Cherri



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