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Avro >> mail # user >> Primitive type aliases


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Re: Primitive type aliases
% grep aliases lang/py/src/avro/*.py
%

I don't see any support for aliases in Python.

Doug
On Fri, Apr 12, 2013 at 2:22 PM, Jeremy Kahn <[EMAIL PROTECTED]> wrote:

> This annotation behavior would be very useful for representing things like
> "age" (a non-negative number), URI (constrained subset of "string") etc.
>
> Doug, when you say "Python doesn't support aliases", what do you mean?
> What behavior should it support? I understood aliases to be only used in
> schema evolution, and the Python avro libraries seem to correctly respect
> aliases when reading from another schema... or don't they?
>
> --Jeremy
>
>
>
>
> On Fri, Apr 12, 2013 at 2:09 PM, Doug Cutting <[EMAIL PROTECTED]> wrote:
>
>> Aliases are used for for type names (records, enums, & fixed) and field
>> names.  Also, I don't think aliases are implemented in Python.
>>
>> You could define a Date record with a single string and use it.  Records
>> have no storage overhead, so this will result in the same serialized form
>> as a string field.  If you don't want the nested structure in memory, then
>> perhaps we should consider an "inline" schema annotation.  This might look
>> like:
>>
>> {"type":"record", "name":"Date", "inline":true,
>> "fields":[{"name":"value", "type":"string"}]}
>> {"type":"record", "name":"Test", "fields":[{"name":"date",
>> "type":"Date"}]}
>>
>> Then the Python implementation might be altered so that when it reads an
>> inline record with a single field then it returns the value of that single
>> field, and similarly accepts a value of the field on write.  This would be
>> a representation-hint to the runtime, and would not affect the schema
>> language or serialization so should be completely compatible.
>>
>> Thoughts?
>>
>> Doug
>>
>>
>>
>> On Fri, Apr 12, 2013 at 12:15 PM, Jay Hacker <[EMAIL PROTECTED]>wrote:
>>
>>> I'd like to be able to alias primitive types, for example to indicate
>>> that a field of type "date" is really a string that I should treat
>>> specially.  The spec says "Named types and fields may have aliases," which
>>> suggests it ought to work ("string" is a named type...).
>>>
>>> I don't really know how to express an alias for a primitive, but things
>>> like this:
>>>
>>> {
>>>     "type": "record",
>>>     "name": "alias-test",
>>>     "fields": [
>>>         {"name": "start", "type": {"type": "string", "aliases":
>>> ["date"]}},
>>>         {"name": "end",   "type": "date"}
>>>     ]
>>> }
>>>
>>> don't work (at least not in the Python 1.7.4 implementation: 'Type
>>> property "date" not a valid Avro schema').  How can I alias a primitive
>>> type, and if not, why not?
>>>
>>> Thanks.
>>>
>>>
>>
>