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Avro >> mail # user >> Exposing a constant in an Avro Schema


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Andrew Kenworthy 2011-11-14, 16:03
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Re: Exposing a constant in an Avro Schema
Named types (records, fields, fixed, enum) can store arbitrary user
properties attached to the schema ( similar to "doc" but no special
meaning).

Do you want this constant to be in every instance of your data object?  If
so, the enum is one way to do it.
If you simply want to push metadata along with the schema, use the schema
properties, they are name-value pairs.  For example you can have "myVersion"
attached to your schema for a record:

{"type":"record", "name":"bar.baz.FooRecord", "myVersion":"1.1", "fields": {
    {"name":"field1", "type":"int"},
    Š
  }
}

On 11/14/11 8:03 AM, "Andrew Kenworthy" <[EMAIL PROTECTED]> wrote:

> Hi,
>
> I would like to "embed" a schema version number in the schema that I use for
> writing data: it would be read-only so that I can determine later on which
> version of my avro schema was used. The best I could come up with is to
> (ab)use an enum with a single value like this, as I couldn't find any way to
> define a constant:
>
> {"type":"enum","name":"version_1_1","doc":"enum indicating avro write schema
> version 1.1","symbols":["VERSION_1_1"]}
>
> Is there a better way to register a constant value that has no meaning within
> the avro data file, other than to expose some kind of meta information?
>
> Thanks,
>
> Andrew Kenworthy
>
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Andrew Kenworthy 2011-11-15, 09:14