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Schema Evolution
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schema_evolution
Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Apache Fory™ supports schema evolution in Compatible mode, allowing fields to be added/removed while maintaining compatibility.

Enable Compatible Mode

import pyfory

f = pyfory.Fory(xlang=True, compatible=True)

Disable Evolution for Stable Classes

If a dataclass schema is stable and will not change, you can disable evolution for that class to avoid compatible metadata overhead. Use pyfory.dataclass with evolving=False:

import pyfory

@pyfory.dataclass(evolving=False)
class StableMessage:
    id: int
    name: str

pyfory.dataclass also supports slots=True:

@pyfory.dataclass(slots=True)
class SlotMessage:
    id: int

Schema Evolution Example

import pyfory
from dataclasses import dataclass

# Version 1: Original class
@dataclass
class User:
    name: str
    age: int

f = pyfory.Fory(xlang=True, compatible=True)
f.register(User, typename="User")
data = f.dumps(User("Alice", 30))

# Version 2: Add new field (backward compatible)
@dataclass
class User:
    name: str
    age: int
    email: str = "unknown@example.com"  # New field with default

# Can still deserialize old data
user = f.loads(data)
print(user.email)  # "unknown@example.com"

Supported Changes

  • Add new fields: With default values
  • Remove fields: Old data with extra fields will be skipped
  • Reorder fields: Fields are matched by name, not position

Best Practices

  1. Always provide default values for new fields
  2. Use typename for cross-language compatibility
  3. Test schema changes before deploying
  4. Document schema versions for your team

Related Topics