First of all, thank you for this project. I love Avro encoding from both technology and code culture points of view.
I know you recommend migrating schema by adding a new field and removing the old one in the future, but please-please-please consider my case as well.
In my company, we have some DTOs, and it's about 200+ fields in total that we encode with Avro and send over the network. About a third of them have type `java.math.BigDecimal`. At some point, we discovered we send them with a schema like
That's a kind of disaster for us cos we have pretty much a high load with ~2 million RPS.
So we start to think about migrating to something lighter than strings (no blame for choosing it as a default, I know BigDecimal has a lot of pitfalls, and string is the easiest way for encoding/decoding).
It was fine to make a standard precision for all such fields, so we found `Conversions.DecimalConversion` and decided at the end of the day we were going to use this logical type with a recommended schema like
(we use `org.apache.avro.reflect.ReflectData`)
It all looks good and promising, but the question is how to migrate to such schema?
As I said, we have a lot of such fields, and migrating all of them with duplication fields with future removal might be painful and would cost us a considerable overhead.
I made some tests and found out if two applications register the same `BigDecimalConversion` but for one application the `getRecommendedSchema()` is like the method above and for another application the `getRecommendedSchema()` is
so they can easily read each other messages using SERVER schema.
So, I made two applications and wired them up with `ProtocolRepository`, `ReflectResponder` and all that stuff, I found out it doesn't work. Because `org.apache.avro.io.ResolvingDecoder` totally ignores logical types for some reason.
So as a result, one application specifically told "I encode this field as a byte array which supposed to be a logical type 'decimal' with precision N", but another application just tries to convert those bytes to a string and make a BigDecimal based on the result string. As a result, we got
In my humble opinion, `org.apache.avro.io.ResolvingDecoder` should respect logical types in SERVER (ACTUAL) schema and use a corresponding conversion instance for reading values. In my example, I'd say it might be
I'd love to read your opinion on all of that.
Thank you in advance for your time, and sorry for the long issue description.