[jira] [Commented] (AVRO-1340) use default to allow old readers to specify default enum value when encountering new enum symbols

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-1340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16394600#comment-16394600 ] 

ASF GitHub Bot commented on AVRO-1340:
--------------------------------------

bellemare opened a new pull request #298: AVRO-1340: Added Enum Defaults and unit tests.
URL: https://github.com/apache/avro/pull/298
 
 
   - Added Enums to Defaults.
   - Enum Defaults are only applied to values which don't match the enum symbols.
   - Enum Defaults do not override any Field Default behaviour. Field Defaults are used when a reader reads a datum that does not have the Field defined (as is current behaviour).
   
   To see an example table of this behaviour, see Final Default & Fallback tab in:
   https://docs.google.com/spreadsheets/d/1YkTBnHCBPGz2t0gQI3OioKS_xP9h9lq_a-gS2jSGFAc/edit?usp=sharing
   
   

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> use default to allow old readers to specify default enum value when encountering new enum symbols
> -------------------------------------------------------------------------------------------------
>
>                 Key: AVRO-1340
>                 URL: https://issues.apache.org/jira/browse/AVRO-1340
>             Project: Avro
>          Issue Type: Improvement
>          Components: spec
>         Environment: N/A
>            Reporter: Jim Donofrio
>            Priority: Minor
>
> The schema resolution page says:
> > if both are enums:
> > if the writer's symbol is not present in the reader's enum, then an
> error is signalled.
> This makes it difficult to use enum's because you can never add a enum value and keep old reader's compatible. Why not use the default option to refer to one of enum values so that when a old reader encounters a enum ordinal it does not recognize, it can default to the optional schema provided one. If the old schema does not provide a default then the older reader can continue to fail as it does today.



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