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# odmantic.session

Bases: `AIOSessionBase`, `AsyncContextManager`

An AsyncIO session object for ordering sequential operations.

Sessions can be created from the engine directly by using the AIOEngine.session method.

Example usage as a context manager:

    engine = AIOEngine(...)
    async with engine.session() as session:
        john = await session.find(User, User.name == "John")
        john.name = "Doe"
        await session.save(john)

Example raw usage:

    engine = AIOEngine(...)
    session = engine.session()
    await session.start()
    john = await session.find(User, User.name == "John")
    john.name = "Doe"
    await session.save(john)
    await session.end()

Source code in `odmantic/session.py`

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    class AIOSession(AIOSessionBase, AsyncContextManager):
        """An AsyncIO session object for ordering sequential operations.

        Sessions can be created from the engine directly by using the
        [AIOEngine.session][odmantic.engine.AIOEngine.session] method.

        Example usage as a context manager:
        ```python
        engine = AIOEngine(...)
        async with engine.session() as session:
            john = await session.find(User, User.name == "John")
            john.name = "Doe"
            await session.save(john)
        ```

        Example raw usage:
        ```python
        engine = AIOEngine(...)
        session = engine.session()
        await session.start()
        john = await session.find(User, User.name == "John")
        john.name = "Doe"
        await session.save(john)
        await session.end()
        ```
        """

        def __init__(self, engine: ODMEngine.AIOEngine):
            self.engine = engine
            self.session: Optional[AsyncIOMotorClientSession] = None

        @property
        def is_started(self) -> bool:
            return self.session is not None

        def get_driver_session(self) -> AsyncIOMotorClientSession:
            """Return the underlying Motor Session"""
            if self.session is None:
                raise RuntimeError("session not started")
            return self.session

        async def start(self) -> None:
            """Start the logical Mongo session."""
            if self.is_started:
                raise RuntimeError("Session is already started")
            self.session = await self.engine.client.start_session()

        async def end(self) -> None:
            """Finish the logical session."""
            if self.session is None:
                raise RuntimeError("Session is not started")
            await self.session.end_session()
            self.session = None

        async def __aenter__(self) -> "AIOSession":
            await self.start()
            return self

        async def __aexit__(
            self,
            exc_type: Optional[Type[BaseException]],
            exc: Optional[BaseException],
            traceback: Optional[TracebackType],
        ) -> None:
            await self.end()

        def transaction(self) -> AIOTransaction:
            """Create a transaction in the existing session"""
            return AIOTransaction(self)

## `end()` `async`

Finish the logical session.

Source code in `odmantic/session.py`

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    async def end(self) -> None:
        """Finish the logical session."""
        if self.session is None:
            raise RuntimeError("Session is not started")
        await self.session.end_session()
        self.session = None

## `get_driver_session()`

Return the underlying Motor Session

Source code in `odmantic/session.py`

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    def get_driver_session(self) -> AsyncIOMotorClientSession:
        """Return the underlying Motor Session"""
        if self.session is None:
            raise RuntimeError("session not started")
        return self.session

## `start()` `async`

Start the logical Mongo session.

Source code in `odmantic/session.py`

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    async def start(self) -> None:
        """Start the logical Mongo session."""
        if self.is_started:
            raise RuntimeError("Session is already started")
        self.session = await self.engine.client.start_session()

## `transaction()`

Create a transaction in the existing session

Source code in `odmantic/session.py`

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    def transaction(self) -> AIOTransaction:
        """Create a transaction in the existing session"""
        return AIOTransaction(self)

Bases: `AIOSessionBase`, `AsyncContextManager`

A transaction object to aggregate sequential operations.

Transactions can be created from the engine using the AIOEngine.transaction method or they can be created during an existing session by using AIOSession.transaction.

Example usage as a context manager:

    engine = AIOEngine(...)
    async with engine.transaction() as transaction:
        john = await transaction.find(User, User.name == "John")
        john.name = "Doe"
        await transaction.save(john)
        await transaction.commit()

Example raw usage:

    engine = AIOEngine(...)
    transaction = engine.transaction()
    await transaction.start()
    john = await transaction.find(User, User.name == "John")
    john.name = "Doe"
    await transaction.save(john)
    await transaction.commit()

Warning

MongoDB transaction are only supported on replicated clusters: either directly a replicaSet or a sharded cluster with replication enabled.

Source code in `odmantic/session.py`

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    class AIOTransaction(AIOSessionBase, AsyncContextManager):
        """A transaction object to aggregate sequential operations.

        Transactions can be created from the engine using the
        [AIOEngine.transaction][odmantic.engine.AIOEngine.transaction]
        method or they can be created during an existing session by using
        [AIOSession.transaction][odmantic.session.AIOSession.transaction].

        Example usage as a context manager:
        ```python
        engine = AIOEngine(...)
        async with engine.transaction() as transaction:
            john = await transaction.find(User, User.name == "John")
            john.name = "Doe"
            await transaction.save(john)
            await transaction.commit()
        ```

        Example raw usage:
        ```python
        engine = AIOEngine(...)
        transaction = engine.transaction()
        await transaction.start()
        john = await transaction.find(User, User.name == "John")
        john.name = "Doe"
        await transaction.save(john)
        await transaction.commit()
        ```

        Warning:
            MongoDB transaction are only supported on replicated clusters: either directly a
            replicaSet or a sharded cluster with replication enabled.
        """

        def __init__(self, context: Union[ODMEngine.AIOEngine, ODMEngine.AIOSession]):
            self._session_provided = isinstance(context, ODMEngine.AIOSession)
            if self._session_provided:
                assert isinstance(context, ODMEngine.AIOSession)
                if not context.is_started:
                    raise RuntimeError("provided session is not started")
                self.session = context
                self.engine = context.engine
            else:
                assert isinstance(context, ODMEngine.AIOEngine)
                self.session = AIOSession(context)
                self.engine = context

            self._transaction_started = False
            self._transaction_context: Optional[AsyncContextManager] = None

        def get_driver_session(self) -> AsyncIOMotorClientSession:
            """Return the underlying Motor Session"""
            if not self._transaction_started:
                raise RuntimeError("transaction not started")
            return self.session.get_driver_session()

        async def start(self) -> None:
            """Initiate the transaction."""
            if self._transaction_started:
                raise RuntimeError("Transaction already started")
            if not self._session_provided:
                await self.session.start()
            assert self.session.session is not None
            self._transaction_context = (
                await self.session.session.start_transaction().__aenter__()
            )
            self._transaction_started = True

        async def commit(self) -> None:
            """Commit the changes and close the transaction."""
            if not self._transaction_started:
                raise RuntimeError("Transaction not started")
            assert self.session.session is not None
            await self.session.session.commit_transaction()
            self._transaction_started = False
            if not self._session_provided:
                await self.session.end()

        async def abort(self) -> None:
            """Discard the changes and drop the transaction"""
            if not self._transaction_started:
                raise RuntimeError("Transaction not started")
            assert self.session.session is not None
            await self.session.session.abort_transaction()
            self._transaction_started = False
            if not self._session_provided:
                await self.session.end()

        async def __aenter__(self) -> "AIOTransaction":
            await self.start()
            return self

        async def __aexit__(
            self,
            exc_type: Optional[Type[BaseException]],
            exc: Optional[BaseException],
            traceback: Optional[TracebackType],
        ) -> None:
            assert self._transaction_context is not None
            await self._transaction_context.__aexit__(exc_type, exc, traceback)
            self._transaction_started = False

## `abort()` `async`

Discard the changes and drop the transaction

Source code in `odmantic/session.py`

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    async def abort(self) -> None:
        """Discard the changes and drop the transaction"""
        if not self._transaction_started:
            raise RuntimeError("Transaction not started")
        assert self.session.session is not None
        await self.session.session.abort_transaction()
        self._transaction_started = False
        if not self._session_provided:
            await self.session.end()

## `commit()` `async`

Commit the changes and close the transaction.

Source code in `odmantic/session.py`

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    async def commit(self) -> None:
        """Commit the changes and close the transaction."""
        if not self._transaction_started:
            raise RuntimeError("Transaction not started")
        assert self.session.session is not None
        await self.session.session.commit_transaction()
        self._transaction_started = False
        if not self._session_provided:
            await self.session.end()

## `get_driver_session()`

Return the underlying Motor Session

Source code in `odmantic/session.py`

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    def get_driver_session(self) -> AsyncIOMotorClientSession:
        """Return the underlying Motor Session"""
        if not self._transaction_started:
            raise RuntimeError("transaction not started")
        return self.session.get_driver_session()

## `start()` `async`

Initiate the transaction.

Source code in `odmantic/session.py`

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    async def start(self) -> None:
        """Initiate the transaction."""
        if self._transaction_started:
            raise RuntimeError("Transaction already started")
        if not self._session_provided:
            await self.session.start()
        assert self.session.session is not None
        self._transaction_context = (
            await self.session.session.start_transaction().__aenter__()
        )
        self._transaction_started = True

Source code in `odmantic/session.py`

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    class AIOSessionBase(metaclass=ABCMeta):
        engine: ODMEngine.AIOEngine

        def find(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[
                QueryExpression, Dict, bool
            ],  # bool: allow using binary operators with mypy
            sort: Optional[Any] = None,
            skip: int = 0,
            limit: Optional[int] = None,
        ) -> ODMEngine.AIOCursor[ODMEngine.ModelType]:
            """Search for Model instances matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                sort: sort expression
                skip: number of document to skip
                limit: maximum number of instance fetched

            Returns:
                [odmantic.engine.AIOCursor][] of the query

            """
            return self.engine.find(
                model,
                *queries,
                sort=sort,
                skip=skip,
                limit=limit,
                session=self.engine._get_session(self),
            )

        async def find_one(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[
                QueryExpression, Dict, bool
            ],  # bool: allow using binary operators w/o plugin
            sort: Optional[Any] = None,
        ) -> Optional[ODMEngine.ModelType]:
            """Search for a Model instance matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                sort: sort expression

            Raises:
                DocumentParsingError: unable to parse the resulting document

            Returns:
                the fetched instance if found otherwise None

            <!---
            #noqa: DAR402 DocumentParsingError
            -->
            """
            return await self.engine.find_one(
                model, *queries, sort=sort, session=self.engine._get_session(self)
            )

        async def count(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[QueryExpression, Dict, bool],
        ) -> int:
            """Get the count of documents matching a query

            Args:
                model: model to perform the operation on
                *queries: query filters to apply

            Returns:
                number of document matching the query
            """
            return await self.engine.count(
                model, *queries, session=self.engine._get_session(self)
            )

        async def save(
            self,
            instance: ODMEngine.ModelType,
        ) -> ODMEngine.ModelType:
            """Persist an instance to the database

            This method behaves as an 'upsert' operation. If a document already exists
            with the same primary key, it will be overwritten.

            All the other models referenced by this instance will be saved as well.

            Args:
                instance: instance to persist

            Returns:
                the saved instance

            NOTE:
                The save operation actually modify the instance argument in place. However,
                the instance is still returned for convenience.
            """
            return await self.engine.save(instance, session=self.engine._get_session(self))

        async def save_all(
            self,
            instances: Sequence[ODMEngine.ModelType],
        ) -> List[ODMEngine.ModelType]:
            """Persist instances to the database

            This method behaves as multiple 'upsert' operations. If one of the document
            already exists with the same primary key, it will be overwritten.

            All the other models referenced by this instance will be recursively saved as
            well.

            Args:
                instances: instances to persist

            Returns:
                the saved instances

            NOTE:
                The save_all operation actually modify the arguments in place. However, the
                instances are still returned for convenience.
            """
            return await self.engine.save_all(
                instances, session=self.engine._get_session(self)
            )

        async def delete(
            self,
            instance: ODMEngine.ModelType,
        ) -> None:
            """Delete an instance from the database

            Args:
                instance: the instance to delete

            Raises:
                DocumentNotFoundError: the instance has not been persisted to the database

            <!---
            #noqa: DAR402 DocumentNotFoundError
            #noqa: DAR201
            -->
            """
            return await self.engine.delete(
                instance, session=self.engine._get_session(self)
            )

        async def remove(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[QueryExpression, Dict, bool],
            just_one: bool = False,
        ) -> int:
            """Delete Model instances matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                just_one: limit the deletion to just one document

            Returns:
                the number of instances deleted from the database.
            """
            return await self.engine.remove(
                model, *queries, just_one=just_one, session=self.engine._get_session(self)
            )

## `count(model, *queries)` `async`

Get the count of documents matching a query

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filters to apply | `()`

Returns:

Type | Description
--- | ---
`int` | number of document matching the query

Source code in `odmantic/session.py`

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    async def count(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[QueryExpression, Dict, bool],
    ) -> int:
        """Get the count of documents matching a query

        Args:
            model: model to perform the operation on
            *queries: query filters to apply

        Returns:
            number of document matching the query
        """
        return await self.engine.count(
            model, *queries, session=self.engine._get_session(self)
        )

## `delete(instance)` `async`

Delete an instance from the database

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instance` | `ModelType` | the instance to delete | required

Raises:

Type | Description
--- | ---
`DocumentNotFoundError` | the instance has not been persisted to the database

Source code in `odmantic/session.py`

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    async def delete(
        self,
        instance: ODMEngine.ModelType,
    ) -> None:
        """Delete an instance from the database

        Args:
            instance: the instance to delete

        Raises:
            DocumentNotFoundError: the instance has not been persisted to the database

        <!---
        #noqa: DAR402 DocumentNotFoundError
        #noqa: DAR201
        -->
        """
        return await self.engine.delete(
            instance, session=self.engine._get_session(self)
        )

## `find(model, *queries, sort=None, skip=0, limit=None)`

Search for Model instances matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`sort` | `Optional[Any]` | sort expression | `None`
`skip` | `int` | number of document to skip | `0`
`limit` | `Optional[int]` | maximum number of instance fetched | `None`

Returns:

Type | Description
--- | ---
`AIOCursor[ModelType]` | odmantic.engine.AIOCursor of the query

Source code in `odmantic/session.py`

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    def find(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[
            QueryExpression, Dict, bool
        ],  # bool: allow using binary operators with mypy
        sort: Optional[Any] = None,
        skip: int = 0,
        limit: Optional[int] = None,
    ) -> ODMEngine.AIOCursor[ODMEngine.ModelType]:
        """Search for Model instances matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            sort: sort expression
            skip: number of document to skip
            limit: maximum number of instance fetched

        Returns:
            [odmantic.engine.AIOCursor][] of the query

        """
        return self.engine.find(
            model,
            *queries,
            sort=sort,
            skip=skip,
            limit=limit,
            session=self.engine._get_session(self),
        )

## `find_one(model, *queries, sort=None)` `async`

Search for a Model instance matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`sort` | `Optional[Any]` | sort expression | `None`

Raises:

Type | Description
--- | ---
`DocumentParsingError` | unable to parse the resulting document

Returns:

Type | Description
--- | ---
`Optional[ModelType]` | the fetched instance if found otherwise None

Source code in `odmantic/session.py`

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    async def find_one(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[
            QueryExpression, Dict, bool
        ],  # bool: allow using binary operators w/o plugin
        sort: Optional[Any] = None,
    ) -> Optional[ODMEngine.ModelType]:
        """Search for a Model instance matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            sort: sort expression

        Raises:
            DocumentParsingError: unable to parse the resulting document

        Returns:
            the fetched instance if found otherwise None

        <!---
        #noqa: DAR402 DocumentParsingError
        -->
        """
        return await self.engine.find_one(
            model, *queries, sort=sort, session=self.engine._get_session(self)
        )

## `remove(model, *queries, just_one=False)` `async`

Delete Model instances matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`just_one` | `bool` | limit the deletion to just one document | `False`

Returns:

Type | Description
--- | ---
`int` | the number of instances deleted from the database.

Source code in `odmantic/session.py`

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    async def remove(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[QueryExpression, Dict, bool],
        just_one: bool = False,
    ) -> int:
        """Delete Model instances matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            just_one: limit the deletion to just one document

        Returns:
            the number of instances deleted from the database.
        """
        return await self.engine.remove(
            model, *queries, just_one=just_one, session=self.engine._get_session(self)
        )

## `save(instance)` `async`

Persist an instance to the database

This method behaves as an 'upsert' operation. If a document already exists with the same primary key, it will be overwritten.

All the other models referenced by this instance will be saved as well.

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instance` | `ModelType` | instance to persist | required

Returns:

Type | Description
--- | ---
`ModelType` | the saved instance

NOTE

The save operation actually modify the instance argument in place. However, the instance is still returned for convenience.

Source code in `odmantic/session.py`

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    async def save(
        self,
        instance: ODMEngine.ModelType,
    ) -> ODMEngine.ModelType:
        """Persist an instance to the database

        This method behaves as an 'upsert' operation. If a document already exists
        with the same primary key, it will be overwritten.

        All the other models referenced by this instance will be saved as well.

        Args:
            instance: instance to persist

        Returns:
            the saved instance

        NOTE:
            The save operation actually modify the instance argument in place. However,
            the instance is still returned for convenience.
        """
        return await self.engine.save(instance, session=self.engine._get_session(self))

## `save_all(instances)` `async`

Persist instances to the database

This method behaves as multiple 'upsert' operations. If one of the document already exists with the same primary key, it will be overwritten.

All the other models referenced by this instance will be recursively saved as well.

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instances` | `Sequence[ModelType]` | instances to persist | required

Returns:

Type | Description
--- | ---
`List[ModelType]` | the saved instances

NOTE

The save_all operation actually modify the arguments in place. However, the instances are still returned for convenience.

Source code in `odmantic/session.py`

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    async def save_all(
        self,
        instances: Sequence[ODMEngine.ModelType],
    ) -> List[ODMEngine.ModelType]:
        """Persist instances to the database

        This method behaves as multiple 'upsert' operations. If one of the document
        already exists with the same primary key, it will be overwritten.

        All the other models referenced by this instance will be recursively saved as
        well.

        Args:
            instances: instances to persist

        Returns:
            the saved instances

        NOTE:
            The save_all operation actually modify the arguments in place. However, the
            instances are still returned for convenience.
        """
        return await self.engine.save_all(
            instances, session=self.engine._get_session(self)
        )

Bases: `SyncSessionBase`, `ContextManager`

A session object for ordering sequential operations.

Sessions can be created from the engine directly by using the SyncEngine.session method.

Example usage as a context manager:

    engine = SyncEngine(...)
    with engine.session() as session:
        john = session.find(User, User.name == "John")
        john.name = "Doe"
        session.save(john)

Example raw usage:

    engine = SyncEngine(...)
    session = engine.session()
    session.start()
    john = session.find(User, User.name == "John")
    john.name = "Doe"
    session.save(john)
    session.end()

Source code in `odmantic/session.py`

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    class SyncSession(SyncSessionBase, ContextManager):
        """A session object for ordering sequential operations.

        Sessions can be created from the engine directly by using the
        [SyncEngine.session][odmantic.engine.SyncEngine.session] method.

        Example usage as a context manager:
        ```python
        engine = SyncEngine(...)
        with engine.session() as session:
            john = session.find(User, User.name == "John")
            john.name = "Doe"
            session.save(john)
        ```

        Example raw usage:
        ```python
        engine = SyncEngine(...)
        session = engine.session()
        session.start()
        john = session.find(User, User.name == "John")
        john.name = "Doe"
        session.save(john)
        session.end()
        ```
        """

        def __init__(self, engine: ODMEngine.SyncEngine):
            self.engine = engine
            self.session: Optional[ClientSession] = None

        @property
        def is_started(self) -> bool:
            return self.session is not None

        def get_driver_session(self) -> ClientSession:
            """Return the underlying PyMongo Session"""
            if self.session is None:
                raise RuntimeError("session not started")
            return self.session

        def start(self) -> None:
            """Start the logical session."""
            if self.is_started:
                raise RuntimeError("Session is already started")
            self.session = self.engine.client.start_session()

        def end(self) -> None:
            """Finish the logical session."""
            if self.session is None:
                raise RuntimeError("Session is not started")
            self.session.end_session()
            self.session = None

        def __enter__(self) -> "SyncSession":
            self.start()
            return self

        def __exit__(
            self,
            exc_type: Optional[Type[BaseException]],
            exc: Optional[BaseException],
            traceback: Optional[TracebackType],
        ) -> None:
            self.end()

        def transaction(self) -> SyncTransaction:
            """Create a transaction in the existing session"""
            return SyncTransaction(self)

## `end()`

Finish the logical session.

Source code in `odmantic/session.py`

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    def end(self) -> None:
        """Finish the logical session."""
        if self.session is None:
            raise RuntimeError("Session is not started")
        self.session.end_session()
        self.session = None

## `get_driver_session()`

Return the underlying PyMongo Session

Source code in `odmantic/session.py`

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    def get_driver_session(self) -> ClientSession:
        """Return the underlying PyMongo Session"""
        if self.session is None:
            raise RuntimeError("session not started")
        return self.session

## `start()`

Start the logical session.

Source code in `odmantic/session.py`

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    def start(self) -> None:
        """Start the logical session."""
        if self.is_started:
            raise RuntimeError("Session is already started")
        self.session = self.engine.client.start_session()

## `transaction()`

Create a transaction in the existing session

Source code in `odmantic/session.py`

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    def transaction(self) -> SyncTransaction:
        """Create a transaction in the existing session"""
        return SyncTransaction(self)

Bases: `SyncSessionBase`, `ContextManager`

A transaction object to aggregate sequential operations.

Transactions can be created from the engine using the SyncEngine.transaction method or they can be created during an existing session by using SyncSession.transaction.

Example usage as a context manager:

    engine = SyncEngine(...)
    with engine.transaction() as transaction:
        john = transaction.find(User, User.name == "John")
        john.name = "Doe"
        transaction.save(john)
        transaction.commit()

Example raw usage:

    engine = SyncEngine(...)
    transaction = engine.transaction()
    transaction.start()
    john = transaction.find(User, User.name == "John")
    john.name = "Doe"
    transaction.save(john)
    transaction.commit()

Warning

MongoDB transaction are only supported on replicated clusters: either directly a replicaSet or a sharded cluster with replication enabled.

Source code in `odmantic/session.py`

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    class SyncTransaction(SyncSessionBase, ContextManager):
        """A transaction object to aggregate sequential operations.

        Transactions can be created from the engine using the
        [SyncEngine.transaction][odmantic.engine.SyncEngine.transaction]
        method or they can be created during an existing session by using
        [SyncSession.transaction][odmantic.session.SyncSession.transaction].

        Example usage as a context manager:
        ```python
        engine = SyncEngine(...)
        with engine.transaction() as transaction:
            john = transaction.find(User, User.name == "John")
            john.name = "Doe"
            transaction.save(john)
            transaction.commit()
        ```

        Example raw usage:
        ```python
        engine = SyncEngine(...)
        transaction = engine.transaction()
        transaction.start()
        john = transaction.find(User, User.name == "John")
        john.name = "Doe"
        transaction.save(john)
        transaction.commit()
        ```

        Warning:
            MongoDB transaction are only supported on replicated clusters: either directly a
            replicaSet or a sharded cluster with replication enabled.
        """

        def __init__(self, context: Union[ODMEngine.SyncEngine, ODMEngine.SyncSession]):
            self._session_provided = isinstance(context, ODMEngine.SyncSession)
            if self._session_provided:
                assert isinstance(context, ODMEngine.SyncSession)
                if not context.is_started:
                    raise RuntimeError("provided session is not started")
                self.session = context
                self.engine = context.engine
            else:
                assert isinstance(context, ODMEngine.SyncEngine)
                self.session = SyncSession(context)
                self.engine = context

            self._transaction_started = False
            self._transaction_context: Optional[ContextManager] = None

        def get_driver_session(self) -> ClientSession:
            """Return the underlying PyMongo Session"""
            if not self._transaction_started:
                raise RuntimeError("transaction not started")
            return self.session.get_driver_session()

        def start(self) -> None:
            """Initiate the transaction."""
            if self._transaction_started:
                raise RuntimeError("Transaction already started")
            if not self._session_provided:
                self.session.start()
            assert self.session.session is not None
            self._transaction_context = self.session.session.start_transaction().__enter__()
            self._transaction_started = True

        def commit(self) -> None:
            """Commit the changes and close the transaction."""
            if not self._transaction_started:
                raise RuntimeError("Transaction not started")
            assert self.session.session is not None
            self.session.session.commit_transaction()
            self._transaction_started = False
            if not self._session_provided:
                self.session.end()

        def abort(self) -> None:
            """Discard the changes and drop the transaction."""
            if not self._transaction_started:
                raise RuntimeError("Transaction not started")
            assert self.session.session is not None
            self.session.session.abort_transaction()
            self._transaction_started = False
            if not self._session_provided:
                self.session.end()

        def __enter__(self) -> "SyncTransaction":
            self.start()
            return self

        def __exit__(
            self,
            exc_type: Optional[Type[BaseException]],
            exc: Optional[BaseException],
            traceback: Optional[TracebackType],
        ) -> None:
            assert self._transaction_context is not None
            self._transaction_context.__exit__(exc_type, exc, traceback)
            self._transaction_started = False

## `abort()`

Discard the changes and drop the transaction.

Source code in `odmantic/session.py`

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    def abort(self) -> None:
        """Discard the changes and drop the transaction."""
        if not self._transaction_started:
            raise RuntimeError("Transaction not started")
        assert self.session.session is not None
        self.session.session.abort_transaction()
        self._transaction_started = False
        if not self._session_provided:
            self.session.end()

## `commit()`

Commit the changes and close the transaction.

Source code in `odmantic/session.py`

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    def commit(self) -> None:
        """Commit the changes and close the transaction."""
        if not self._transaction_started:
            raise RuntimeError("Transaction not started")
        assert self.session.session is not None
        self.session.session.commit_transaction()
        self._transaction_started = False
        if not self._session_provided:
            self.session.end()

## `get_driver_session()`

Return the underlying PyMongo Session

Source code in `odmantic/session.py`

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    def get_driver_session(self) -> ClientSession:
        """Return the underlying PyMongo Session"""
        if not self._transaction_started:
            raise RuntimeError("transaction not started")
        return self.session.get_driver_session()

## `start()`

Initiate the transaction.

Source code in `odmantic/session.py`

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    def start(self) -> None:
        """Initiate the transaction."""
        if self._transaction_started:
            raise RuntimeError("Transaction already started")
        if not self._session_provided:
            self.session.start()
        assert self.session.session is not None
        self._transaction_context = self.session.session.start_transaction().__enter__()
        self._transaction_started = True

Source code in `odmantic/session.py`

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    class SyncSessionBase(metaclass=ABCMeta):
        engine: ODMEngine.SyncEngine

        def find(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[
                QueryExpression, Dict, bool
            ],  # bool: allow using binary operators with mypy
            sort: Optional[Any] = None,
            skip: int = 0,
            limit: Optional[int] = None,
        ) -> ODMEngine.SyncCursor[ODMEngine.ModelType]:
            """Search for Model instances matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                sort: sort expression
                skip: number of document to skip
                limit: maximum number of instance fetched

            Returns:
                [odmantic.engine.SyncCursor][] of the query

            """
            return self.engine.find(
                model,
                *queries,
                sort=sort,
                skip=skip,
                limit=limit,
                session=self.engine._get_session(self),
            )

        def find_one(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[
                QueryExpression, Dict, bool
            ],  # bool: allow using binary operators w/o plugin
            sort: Optional[Any] = None,
        ) -> Optional[ODMEngine.ModelType]:
            """Search for a Model instance matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                sort: sort expression

            Raises:
                DocumentParsingError: unable to parse the resulting document

            Returns:
                the fetched instance if found otherwise None

            <!---
            #noqa: DAR402 DocumentParsingError
            -->
            """
            return self.engine.find_one(
                model, *queries, sort=sort, session=self.engine._get_session(self)
            )

        def count(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[QueryExpression, Dict, bool],
        ) -> int:
            """Get the count of documents matching a query

            Args:
                model: model to perform the operation on
                *queries: query filters to apply

            Returns:
                number of document matching the query
            """
            return self.engine.count(
                model, *queries, session=self.engine._get_session(self)
            )

        def save(
            self,
            instance: ODMEngine.ModelType,
        ) -> ODMEngine.ModelType:
            """Persist an instance to the database

            This method behaves as an 'upsert' operation. If a document already exists
            with the same primary key, it will be overwritten.

            All the other models referenced by this instance will be saved as well.

            Args:
                instance: instance to persist

            Returns:
                the saved instance

            NOTE:
                The save operation actually modify the instance argument in place. However,
                the instance is still returned for convenience.
            """
            return self.engine.save(instance, session=self.engine._get_session(self))

        def save_all(
            self,
            instances: Sequence[ODMEngine.ModelType],
        ) -> List[ODMEngine.ModelType]:
            """Persist instances to the database

            This method behaves as multiple 'upsert' operations. If one of the document
            already exists with the same primary key, it will be overwritten.

            All the other models referenced by this instance will be recursively saved as
            well.

            Args:
                instances: instances to persist

            Returns:
                the saved instances

            NOTE:
                The save_all operation actually modify the arguments in place. However, the
                instances are still returned for convenience.
            """
            return self.engine.save_all(instances, session=self.engine._get_session(self))

        def delete(
            self,
            instance: ODMEngine.ModelType,
        ) -> None:
            """Delete an instance from the database

            Args:
                instance: the instance to delete

            Raises:
                DocumentNotFoundError: the instance has not been persisted to the database

            <!---
            #noqa: DAR402 DocumentNotFoundError
            #noqa: DAR201
            -->
            """
            return self.engine.delete(instance, session=self.engine._get_session(self))

        def remove(
            self,
            model: Type[ODMEngine.ModelType],
            *queries: Union[QueryExpression, Dict, bool],
            just_one: bool = False,
        ) -> int:
            """Delete Model instances matching the query filter provided

            Args:
                model: model to perform the operation on
                *queries: query filter to apply
                just_one: limit the deletion to just one document

            Returns:
                the number of instances deleted from the database.

            """
            return self.engine.remove(
                model, *queries, just_one=just_one, session=self.engine._get_session(self)
            )

## `count(model, *queries)`

Get the count of documents matching a query

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filters to apply | `()`

Returns:

Type | Description
--- | ---
`int` | number of document matching the query

Source code in `odmantic/session.py`

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    def count(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[QueryExpression, Dict, bool],
    ) -> int:
        """Get the count of documents matching a query

        Args:
            model: model to perform the operation on
            *queries: query filters to apply

        Returns:
            number of document matching the query
        """
        return self.engine.count(
            model, *queries, session=self.engine._get_session(self)
        )

## `delete(instance)`

Delete an instance from the database

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instance` | `ModelType` | the instance to delete | required

Raises:

Type | Description
--- | ---
`DocumentNotFoundError` | the instance has not been persisted to the database

Source code in `odmantic/session.py`

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    def delete(
        self,
        instance: ODMEngine.ModelType,
    ) -> None:
        """Delete an instance from the database

        Args:
            instance: the instance to delete

        Raises:
            DocumentNotFoundError: the instance has not been persisted to the database

        <!---
        #noqa: DAR402 DocumentNotFoundError
        #noqa: DAR201
        -->
        """
        return self.engine.delete(instance, session=self.engine._get_session(self))

## `find(model, *queries, sort=None, skip=0, limit=None)`

Search for Model instances matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`sort` | `Optional[Any]` | sort expression | `None`
`skip` | `int` | number of document to skip | `0`
`limit` | `Optional[int]` | maximum number of instance fetched | `None`

Returns:

Type | Description
--- | ---
`SyncCursor[ModelType]` | odmantic.engine.SyncCursor of the query

Source code in `odmantic/session.py`

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    def find(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[
            QueryExpression, Dict, bool
        ],  # bool: allow using binary operators with mypy
        sort: Optional[Any] = None,
        skip: int = 0,
        limit: Optional[int] = None,
    ) -> ODMEngine.SyncCursor[ODMEngine.ModelType]:
        """Search for Model instances matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            sort: sort expression
            skip: number of document to skip
            limit: maximum number of instance fetched

        Returns:
            [odmantic.engine.SyncCursor][] of the query

        """
        return self.engine.find(
            model,
            *queries,
            sort=sort,
            skip=skip,
            limit=limit,
            session=self.engine._get_session(self),
        )

## `find_one(model, *queries, sort=None)`

Search for a Model instance matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`sort` | `Optional[Any]` | sort expression | `None`

Raises:

Type | Description
--- | ---
`DocumentParsingError` | unable to parse the resulting document

Returns:

Type | Description
--- | ---
`Optional[ModelType]` | the fetched instance if found otherwise None

Source code in `odmantic/session.py`

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    def find_one(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[
            QueryExpression, Dict, bool
        ],  # bool: allow using binary operators w/o plugin
        sort: Optional[Any] = None,
    ) -> Optional[ODMEngine.ModelType]:
        """Search for a Model instance matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            sort: sort expression

        Raises:
            DocumentParsingError: unable to parse the resulting document

        Returns:
            the fetched instance if found otherwise None

        <!---
        #noqa: DAR402 DocumentParsingError
        -->
        """
        return self.engine.find_one(
            model, *queries, sort=sort, session=self.engine._get_session(self)
        )

## `remove(model, *queries, just_one=False)`

Delete Model instances matching the query filter provided

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`model` | `Type[ModelType]` | model to perform the operation on | required
`*queries` | `Union[QueryExpression, Dict, bool]` | query filter to apply | `()`
`just_one` | `bool` | limit the deletion to just one document | `False`

Returns:

Type | Description
--- | ---
`int` | the number of instances deleted from the database.

Source code in `odmantic/session.py`

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    def remove(
        self,
        model: Type[ODMEngine.ModelType],
        *queries: Union[QueryExpression, Dict, bool],
        just_one: bool = False,
    ) -> int:
        """Delete Model instances matching the query filter provided

        Args:
            model: model to perform the operation on
            *queries: query filter to apply
            just_one: limit the deletion to just one document

        Returns:
            the number of instances deleted from the database.

        """
        return self.engine.remove(
            model, *queries, just_one=just_one, session=self.engine._get_session(self)
        )

## `save(instance)`

Persist an instance to the database

This method behaves as an 'upsert' operation. If a document already exists with the same primary key, it will be overwritten.

All the other models referenced by this instance will be saved as well.

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instance` | `ModelType` | instance to persist | required

Returns:

Type | Description
--- | ---
`ModelType` | the saved instance

NOTE

The save operation actually modify the instance argument in place. However, the instance is still returned for convenience.

Source code in `odmantic/session.py`

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    def save(
        self,
        instance: ODMEngine.ModelType,
    ) -> ODMEngine.ModelType:
        """Persist an instance to the database

        This method behaves as an 'upsert' operation. If a document already exists
        with the same primary key, it will be overwritten.

        All the other models referenced by this instance will be saved as well.

        Args:
            instance: instance to persist

        Returns:
            the saved instance

        NOTE:
            The save operation actually modify the instance argument in place. However,
            the instance is still returned for convenience.
        """
        return self.engine.save(instance, session=self.engine._get_session(self))

## `save_all(instances)`

Persist instances to the database

This method behaves as multiple 'upsert' operations. If one of the document already exists with the same primary key, it will be overwritten.

All the other models referenced by this instance will be recursively saved as well.

Parameters:

Name | Type | Description | Default
--- | --- | --- | ---
`instances` | `Sequence[ModelType]` | instances to persist | required

Returns:

Type | Description
--- | ---
`List[ModelType]` | the saved instances

NOTE

The save_all operation actually modify the arguments in place. However, the instances are still returned for convenience.

Source code in `odmantic/session.py`

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    def save_all(
        self,
        instances: Sequence[ODMEngine.ModelType],
    ) -> List[ODMEngine.ModelType]:
        """Persist instances to the database

        This method behaves as multiple 'upsert' operations. If one of the document
        already exists with the same primary key, it will be overwritten.

        All the other models referenced by this instance will be recursively saved as
        well.

        Args:
            instances: instances to persist

        Returns:
            the saved instances

        NOTE:
            The save_all operation actually modify the arguments in place. However, the
            instances are still returned for convenience.
        """
        return self.engine.save_all(instances, session=self.engine._get_session(self))