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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1340) use default to allow old readers to specify default enum value when encountering new enum symbols
Date Thu, 09 Feb 2017 16:40:41 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15859764#comment-15859764
] 

Doug Cutting commented on AVRO-1340:
------------------------------------

A constaint on the design of new schema features is that they be both forward and backward
compatible, unless we wish to trigger a major, Avro 2.0, release.  In this case, an implementation
that did not know about this feature would not be able to read data that used this feature.
 So new enum features cannot alter the syntax or semantics of the "symbols" but should probably
rather add new attributes.

> 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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