Re: Versioning of an array of a record

[Robin Müller]

Thanks for the fast reply.
I use the implementation for avro-serialization from voldemort 
(key-value-store) and it seems that they don't use the ResolvingDecoder. 
But I think there is a way to use an own implementation for the 
serialization in voldemort. So I'll give it a try with the ResolvingDecoder.

Greetings,
Robin

Am 16.09.2010 10:21, schrieb Scott Carey:
Assuming Java:  Are you using a ResolvingDecoder?

This will happen by default if you are reading Generic or Specific records from 
an Avro File, but if you are reading data otherwise, you have to use a 
ResolvingDecoder to specify the expected (reader) and  actual (writer) schemas.

On Sep 16, 2010, at 1:09 AM, Robin Müller wrote:

   
Hi,

I've read the part "Schema Resolution" of the Avro Specification. So I
think that avro supports versioning of the schema.
But when I try to change to following schema, an AvroTypeException will
be thrown by reading data that was serialized with the old schema:
{
   "name":"BrowserCountArray",
   "type":"record",
   "fields": [
     {
     "name":"BrowserCounts",
     "type":
     {
       "type":"array",
       "items": {
         "name": "BrowserCount",
         "type": "record",
         "fields": [
           {
             "name":"Browser",
             "type":"string"
           }, {
             "name":"Count",
             "type":"int"
           }]
         }
       }
     }]
}

For example I add a new field to the BrowserCount record like this:

{
   "name":"BrowserCountArray",
   "type":"record",
   "fields": [
     {
     "name":"BrowserCounts",
     "type":
     {
       "type":"array",
       "items": {
         "name": "BrowserCount",
         "type": "record",
         "fields": [
           {
             "name":"Browser",
             "type":"string"
           }, {
             "name":"Count",
             "type":"int"
           }, {
             "name":"Blub",
             "type":"int",
             "default":"0"
           }]
         }
       }
     }]
}

Is it possible to add or remove fields from this record and read with
this new schema data, that was serialized with an old one.
Or is there another way to define an array of record which solves that
problem.

Thanks,
Robin