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https://issues.apache.org/jira/browse/AVRO-75?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12797936#action_12797936
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Philip Zeyliger commented on AVRO-75:
-------------------------------------
The code answered my own question:
{noformat}
if (actual.getType() == Type.UNION) // resolve unions
actual = actual.getTypes().get((int)in.readIndex());
if (expected.getType() == Type.UNION)
expected = resolveExpected(actual, expected);
{noformat}
A record written with a schema of [string, int] can be read by a schema of
[int] as long as the record only follows the int branch.
It still feels weird to me that schema resolution depends on the data being
resolved. I was going to write an avroj tool tlike "valid_schema_resolution
writer_schema reader_schema", but such a thing would have to depend on the
datum.
> Clarify resolution for enums (and fix code)
> -------------------------------------------
>
> Key: AVRO-75
> URL: https://issues.apache.org/jira/browse/AVRO-75
> Project: Avro
> Issue Type: Bug
> Components: spec
> Reporter: Raymie Stata
> Assignee: Doug Cutting
> Fix For: 1.3.0
>
>
> The current resolution rule for enum's says: "if the writer's symbol is not
> present in the reader's enum, then the enum value is unset." This is the
> only place the word "unset" is used in the doc, it's not clear what you mean.
> The code seems to be inconsistent: GenericDatumReader will happily return a
> symbol the reader doesn't understand; ReflectDatumReader will probably throw
> a class-not-found exception; ResolvingDecoder throws an error.
> I propose that we declare this case an error, i.e., rewrite the spec to "if
> the writer's symbol is not listed in the reader's enum, an error is
> signaled." GenericDatumReader should be updated to throw an error in this
> case.
> If we decide to stick with the "unset" language, we need to define what
> "unset" means (and, if necessary, update ReflectDatumReader and
> ResolvingDecoder).
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