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https://issues.apache.org/jira/browse/AVRO-2199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16645527#comment-16645527
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ASF GitHub Bot commented on AVRO-2199:
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theturtle32 commented on issue #320: AVRO-2199: Validate that field defaults
have the correct type
URL: https://github.com/apache/avro/pull/320#issuecomment-428729499
This has an unfortunate side effect: it breaks applications from reading
existing data that's been encoded with older versions of schemas that had
incompatible default values specified. The library won't even finish parsing
the old schemas, so you can't decode existing data.
The Avro specification says that when you have a union type, any default
value must be of the first type specified in the union. We have millions of
records of data encoded using a schema where the default value was of the
second or third type in the union instead of the first type. This always worked
just fine before but with this more stringent validation, our application
suddenly fails to decode our existing data because it raises an error while
parsing the writer's schema.
I'm going to try to write a monkey-patch to relax this validation
temporarily, long enough to read all existing data, migrate it to a newer
schema, and re-save it. But that's a lot of time and effort to compensate for a
sudden change in schema validation.
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> Validate that field defaults have the correct type
> ---------------------------------------------------
>
> Key: AVRO-2199
> URL: https://issues.apache.org/jira/browse/AVRO-2199
> Project: Avro
> Issue Type: Improvement
> Components: ruby
> Affects Versions: 1.8.2
> Reporter: Daniel Orner
> Priority: Minor
>
> Currently, on the master branch, when a schema is parsed, it is possible to
> define a field with a type and a default of a totally different type. E.g. if
> the field has type "string", the default can be set to "null".
> I'd like to open a PR which will fix this by running the default through the
> SchemaValidator whenever a new Field is created. See
> [https://github.com/salsify/avro-patches/pull/16]
> cc: [~tjwp]
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