Logical type UUID with type "fixed" do not serialize to fixed 16

[Tipnos]

Avro 1.12.0 specifies that UUID logical types annotates to either String or Fixed 16.

The example below serialized the UUID to a String and not a Fixed 16

#[derive(Debug, Serialize, Deserialize)]
struct Comment {
    id: Uuid,
}

impl AvroSchema for Comment {
    fn get_schema() -> Schema {
        Schema::parse_str(
            r#"{
                "type" : "record",
                "name" : "Comment",
                "fields" : [ {
                  "name" : "id",
                  "type" : {
                    "type" : "fixed",
                    "size" : 16,
                    "logicalType" : "uuid",
                    "name": "FixedUUID" // if we remove the name attribute schema parsing fail. The name attribute is not in avro 1.12.0 specification
                  }
                } ]
             }"#,
        )
        .expect("Invalid Comment Avro schema")
    }
}

let payload = Comment {
        id: "de2df598-9948-4988-b00a-a41c0e287398".parse().unwrap(),
};
let mut buffer = Vec::new();
SpecificSingleObjectWriter::<Comment>::with_capacity(10)
    .unwrap()
    .write_ref(&payload, &mut buffer)
    .unwrap();

Do you plan to support it in the near future?

[martin-g]

I will try to take a look next week!
Any help is welcome! Providing a PR will make sure it is supported in nearest future! ;-)

[martin-g]

Added the test case to the suite - #55
It works just fine locally.
I guess it has been fixed with #9

[Tipnos]

I had a look a the test you added, it checks that it serializes successfully but doesn't check the payload content/size to validate that uuid is encoded as 16 bytes.

I just hex dump the content of your test, the payload length is 47 bytes instead of 26.

Why 26:

• 2 bytes of Avro marker
• 8 bytes of schema fingerprint
• 16 bytes for the uuid

In the actual 47 bytes, the UUID takes 37 bytes which is its number of characters.

[martin-g]

This deserves a new issue.
The bug here is that AvroSchema derived Schema does not support logical types at all at the moment ... This was not correct. The issue is somewhere else.

[martin-g]

The problem here is that SpecificSingleObjectWriter::<Comment>::with_capacity(10)?.write_ref(&payload, &mut buffer) uses Serde and Uuid's serde support serializes it to String, i.e. it calls fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error> and without support for external Schema there is no way for the Avro impl to know that it should create apache_avro::types::Value::Fixed instead of apache_avro::types::Value::String and this leads to 37 bytes instead of 16.

If you have idea how to tell Serde to use an external Schema I'll be glad to explore it!

Otherwise I'd suggest to use the avro way.