[AVRO-3814] [Rust] Schema resolution fails when extending a nested record with a union type

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.12.0, 1.11.3
• Component/s: rust
• Labels: pull-request-available

Language

Rust

• Assignee: Martin Tzvetanov Grigorov
• Reporter: Rik Heijdens
• Created: 26/Jul/23 13:39
• Updated: 23/Aug/23 06:52
• Resolved: 15/Aug/23 11:35

Description

Consider the following schema:

{
    "type": "record",
    "name": "MyOuterRecord",
    "fields": [
        {
            "name": "inner_record",
            "type": [
                "null",
                {
                    "type": "record",
                    "name": "MyRecord",
                    "fields": [
                        {"name": "a", "type": "string"}
                    ]
                }
            ],
            "default": null
        }
    ]
}

Over time one might decide to add a new optional enum field 'b' to `MyRecord`, resulting in the following schema:

{
    "type": "record",
    "name": "MyOuterRecord",
    "fields": [
        {
            "name": "inner_record",
            "type": [
                "null",
                {
                    "type": "record",
                    "name": "MyRecord",
                    "fields": [
                        {"name": "a", "type": "string"},
                        {
                            "name": "b",
                            "type": [
                                "null",
                                {
                                    "type": "enum",
                                    "name": "MyEnum",
                                    "symbols": ["A", "B", "C"],
                                    "default": "C"
                                }
                            ],
                            "default": null
                        }
                    ]
                }
            ]
        }
    ],
    "default": null
}

When one then serializes a message with the updated schema, and then attempts to deserialize it using the updated schema, while attempting to resolve it with the earlier schema, then schema resolution in Value::resolve_union() fails with `Error::FindUnionVariant`. This appears to be caused by `UnionSchema.find_schema_with_known_schemata()` failing to resolve the schema appropriately.

I would not expect schema resolution to fail in this case. I will accompany this ticket with a test-case that allows reproduction.

Issue Links

• fixes: AVRO-3786 [Rust] Deserialization results in FindUnionVariant error if the writer and reader have the same symbol but at different positions
• links to: GitHub Pull Request #2394
• links to: GitHub Pull Request #2441