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https://issues.apache.org/jira/browse/AVRO-1340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16460084#comment-16460084
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ASF GitHub Bot commented on AVRO-1340:
--------------------------------------
cutting commented on a change in pull request #298: AVRO-1340: Added Enum
Defaults and unit tests.
URL: https://github.com/apache/avro/pull/298#discussion_r185319837
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File path: doc/src/content/xdocs/idl.xml
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@@ -152,15 +152,29 @@ protocol MyProtocol {
<section id="format_enums">
<title>Defining an Enumeration</title>
<p>
- Enums are defined in Avro IDL using a syntax similar to C or Java:
+ Enums are defined in Avro IDL using a syntax similar to C or Java. An
Avro Enum supports optional default values.
+ In the case that a reader schema is unable to recognize a symbol
written by the writer, the reader will fall back to using the defined default
value.
+ This default is only used when an incompatible symbol is read. It is
not used if the enum field is missing.
+ </p>
+ <p>
+ Example Writer Enum Definition
</p>
<source>
-enum Suit {
- SPADES, DIAMONDS, CLUBS, HEARTS
+enum Shapes {
+ SQUARE, TRIANGLE, CIRCLE, OVAL
}
</source>
<p>
- Note that, unlike the JSON format, anonymous enums cannot be defined.
+ Example Reader Enum Definition
+ </p>
+ <source>
+enum Shapes {
+ SQUARE, TRIANGLE, CIRCLE
+} = CIRCLE
Review comment:
need a semicolon at EOL
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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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