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# Migrations
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Schema migration tools for iterative and free-form data migrations with batch processing support.
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## Capabilities
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### Iterative Migration
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```python { .api }
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def iterative_migration(
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    document_models: List[Type[Document]],
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    batch_size: int = 1000
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):
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    """Decorator for creating iterative data migrations with batching."""
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    ...
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```
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### Free Fall Migration
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```python { .api }
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def free_fall_migration(document_models: List[Type[Document]]):
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    """Decorator for creating free-form migration functions."""
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    ...
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```
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## Usage Examples
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```python
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from beanie import Document, iterative_migration, free_fall_migration
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class User(Document):
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    name: str
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    email: str
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    class Settings:
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        collection = "users"
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@iterative_migration(document_models=[User], batch_size=100)
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async def migrate_user_data():
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    """Add default values for new field."""
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    async for user in User.find({"active": {"$exists": False}}):
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        user.active = True
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        await user.save()
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@free_fall_migration(document_models=[User])
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async def complex_migration():
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    """Complex data transformation."""
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    # Custom migration logic
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    await User.find({"old_field": {"$exists": True}}).update({"$unset": {"old_field": ""}})
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```