# `database` – Database level operations

Database level operations.

pymongo.auth.MECHANISMS = frozenset({'DEFAULT', 'GSSAPI', 'MONGODB-AWS', 'MONGODB-OIDC', 'MONGODB-X509', 'PLAIN', 'SCRAM-SHA-1', 'SCRAM-SHA-256'})

  Build an immutable unordered collection of unique elements.

class pymongo.database.Database(client, name, codec_options=None, read_preference=None, write_concern=None, read_concern=None)

  Get a database by client and name.

  Raises `TypeError` if name is not an instance of `str`. Raises `InvalidName` if name is not a valid database name.

  Parameters:

    - client (MongoClient[_DocumentType]) – A `MongoClient` instance.

    - name (str) – The database name.

    - codec_options (Optional[CodecOptions[_DocumentTypeArg]]) – An instance of `CodecOptions`. If `None` (the default) client.codec_options is used.

    - read_preference (Optional[_ServerMode]) – The read preference to use. If `None` (the default) client.read_preference is used.

    - write_concern (Optional[WriteConcern]) – An instance of `WriteConcern`. If `None` (the default) client.write_concern is used.

    - read_concern (Optional[ReadConcern]) – An instance of `ReadConcern`. If `None` (the default) client.read_concern is used.

  See also

  The MongoDB documentation on databases.

  Changed in version 4.0: Removed the eval, system_js, error, last_status, previous_error, reset_error_history, authenticate, logout, collection_names, current_op, add_user, remove_user, profiling_level, set_profiling_level, and profiling_info methods. See the PyMongo 4 Migration Guide.

  Changed in version 3.2: Added the read_concern option.

  Changed in version 3.0: Added the codec_options, read_preference, and write_concern options. `Database` no longer returns an instance of `Collection` for attribute names with leading underscores. You must use dict-style lookups instead::

  > db[‘__my_collection__’]

  Not:

  > db.__my_collection__

  db[collection_name] || db.collection_name

    Get the collection_name `Collection` of `Database` db.

    Raises `InvalidName` if an invalid collection name is used.

    Note

    Use dictionary style access if collection_name is an attribute of the `Database` class eg: db[collection_name].

  __getitem__(name)

    Get a collection of this database by name.

    Raises InvalidName if an invalid collection name is used.

    Parameters:

      name (str) – the name of the collection to get

    Return type:

      Collection[_DocumentType]

  __getattr__(name)

    Get a collection of this database by name.

    Raises InvalidName if an invalid collection name is used.

    Parameters:

      name (str) – the name of the collection to get

    Return type:

      Collection[_DocumentType]

  codec_options

    Read only access to the `CodecOptions` of this instance.

  read_preference

    Read only access to the read preference of this instance.

    Changed in version 3.0: The `read_preference` attribute is now read only.

  write_concern

    Read only access to the `WriteConcern` of this instance.

    Changed in version 3.0: The `write_concern` attribute is now read only.

  read_concern

    Read only access to the `ReadConcern` of this instance.

    Added in version 3.2.

  aggregate(pipeline, session=None, **kwargs)

    Perform a database-level aggregation.

    See the aggregation pipeline documentation for a list of stages that are supported.

        # Lists all operations currently running on the server.
        with client.admin.aggregate([{"$currentOp": {}}]) as cursor:
            for operation in cursor:
                print(operation)

    The `aggregate()` method obeys the `read_preference` of this `Database`, except when `$out` or `$merge` are used, in which case `PRIMARY` is used.

    Cursors are closed automatically when they are exhausted (the last batch of data is retrieved from the database). If a cursor is not exhausted, it will be closed automatically upon garbage collection, which leaves resources open but unused for a potentially long period of time. To avoid this, best practice is to call `Cursor.close()` when the cursor is no longer needed, or use the cursor in a with statement.

    Note

    This method does not support the ‘explain’ option. Please use `command()` instead.

    Note

    The `write_concern` of this collection is automatically applied to this operation.

    Parameters:

      - pipeline (_Pipeline) – a list of aggregation pipeline stages

      - session (Optional[ClientSession]) – a `ClientSession`.

      - kwargs (Any) – extra aggregate command parameters.

    Return type:

      CommandCursor[_DocumentType]

    All optional aggregate command parameters should be passed as keyword arguments to this method. Valid options include, but are not limited to:

    > - allowDiskUse (bool): Enables writing to temporary files. When set to True, aggregation stages can write data to the _tmp subdirectory of the –dbpath directory. The default is False.

    > - maxTimeMS (int): The maximum amount of time to allow the operation to run in milliseconds.

    > - batchSize (int): The maximum number of documents to return per batch. Ignored if the connected mongod or mongos does not support returning aggregate results using a cursor.

    > - collation (optional): An instance of `Collation`.

    > - let (dict): A dict of parameter names and values. Values must be constant or closed expressions that do not reference document fields. Parameters can then be accessed as variables in an aggregate expression context (e.g. `"$$var"`). This option is only supported on MongoDB >= 5.0.

    Returns:

      A `CommandCursor` over the result set.

    Parameters:

      - pipeline (_Pipeline)

      - session (Optional[ClientSession])

      - kwargs (Any)

    Return type:

      CommandCursor[_DocumentType]

    Added in version 3.9.

  property client: MongoClient[_DocumentType]

    The client instance for this `Database`.

  command(command: str | MutableMapping[str, Any], value: Any = 1, check: bool = True, allowable_errors: Sequence[str | int] | None = None, read_preference: _ServerMode | None = None, codec_options: None = None, session: ClientSession | None = None, comment: Any | None = None, **kwargs: Any) → dict[str, Any]
  command(command: str | MutableMapping[str, Any], value: Any = 1, check: bool = True, allowable_errors: Sequence[str | int] | None = None, read_preference: _ServerMode | None = None, codec_options: CodecOptions[_CodecDocumentType] = None, session: ClientSession | None = None, comment: Any | None = None, **kwargs: Any) → _CodecDocumentType

    Issue a MongoDB command.

    Send command command to the database and return the response. If command is an instance of `str` then the command {command: value} will be sent. Otherwise, command must be an instance of `dict` and will be sent as is.

    Any additional keyword arguments will be added to the final command document before it is sent.

    For example, a command like `{buildinfo: 1}` can be sent using:

        >>> db.command("buildinfo")
        OR
        >>> db.command({"buildinfo": 1})

    For a command where the value matters, like `{count: collection_name}` we can do:

        >>> db.command("count", collection_name)
        OR
        >>> db.command({"count": collection_name})

    For commands that take additional arguments we can use kwargs. So `{count: collection_name, query: query}` becomes:

        >>> db.command("count", collection_name, query=query)
        OR
        >>> db.command({"count": collection_name, "query": query})

    Parameters:

      - command –

        document representing the command to be issued, or the name of the command (for simple commands only).

        Note

        the order of keys in the command document is significant (the “verb” must come first), so commands which require multiple keys (e.g. findandmodify) should be done with this in mind.

      - value – value to use for the command verb when command is passed as a string

      - check – check the response for errors, raising `OperationFailure` if there are any

      - allowable_errors – if check is `True`, error messages in this list will be ignored by error-checking

      - read_preference – The read preference for this operation. See `read_preferences` for options. If the provided session is in a transaction, defaults to the read preference configured for the transaction. Otherwise, defaults to `PRIMARY`.

      - codec_options – A `CodecOptions` instance.

      - session – A `ClientSession`.

      - comment – A user-provided comment to attach to this command.

      - kwargs – additional keyword arguments will be added to the command document before it is sent

    Note

    `command()` does not obey this Database’s `read_preference` or `codec_options`. You must use the `read_preference` and `codec_options` parameters instead.

    Note

    `command()` does not apply any custom TypeDecoders when decoding the command response.

    Note

    If this client has been configured to use MongoDB Stable API (see versioned API), then `command()` will automatically add API versioning options to the given command. Explicitly adding API versioning options in the command and declaring an API version on the client is not supported.

    Changed in version 3.6: Added `session` parameter.

    Changed in version 3.0: Removed the as_class, fields, uuid_subtype, tag_sets, and secondary_acceptable_latency_ms option. Removed compile_re option: PyMongo now always represents BSON regular expressions as `Regex` objects. Use `try_compile()` to attempt to convert from a BSON regular expression to a Python regular expression object. Added the `codec_options` parameter.

    See also

    The MongoDB documentation on commands.

  create_collection(name, codec_options=None, read_preference=None, write_concern=None, read_concern=None, session=None, check_exists=True, **kwargs)

    Create a new `Collection` in this database.

    Normally collection creation is automatic. This method should only be used to specify options on creation. `CollectionInvalid` will be raised if the collection already exists.

    Parameters:

      - name (str) – the name of the collection to create

      - codec_options (Optional[CodecOptions[_DocumentTypeArg]]) – An instance of `CodecOptions`. If `None` (the default) the `codec_options` of this `Database` is used.

      - read_preference (Optional[_ServerMode]) – The read preference to use. If `None` (the default) the `read_preference` of this `Database` is used.

      - write_concern (Optional[WriteConcern]) – An instance of `WriteConcern`. If `None` (the default) the `write_concern` of this `Database` is used.

      - read_concern (Optional[ReadConcern]) – An instance of `ReadConcern`. If `None` (the default) the `read_concern` of this `Database` is used.

      - collation – An instance of `Collation`.

      - session (Optional[ClientSession]) – a `ClientSession`.

      - check_exists (Optional[bool]) – if True (the default), send a listCollections command to check if the collection already exists before creation.

      - kwargs (Any) – additional keyword arguments will be passed as options for the create collection command

    Return type:

      Collection[_DocumentType]

    All optional create collection command parameters should be passed as keyword arguments to this method. Valid options include, but are not limited to:

    > - `size` (int): desired initial size for the collection (in bytes). For capped collections this size is the max size of the collection.

    > - `capped` (bool): if True, this is a capped collection

    > - `max` (int): maximum number of objects if capped (optional)

    > - `timeseries` (dict): a document specifying configuration options for timeseries collections

    > - `expireAfterSeconds` (int): the number of seconds after which a document in a timeseries collection expires

    > - `validator` (dict): a document specifying validation rules or expressions for the collection

    > - `validationLevel` (str): how strictly to apply the validation rules to existing documents during an update. The default level is “strict”

    > - `validationAction` (str): whether to “error” on invalid documents (the default) or just “warn” about the violations but allow invalid documents to be inserted

    > - `indexOptionDefaults` (dict): a document specifying a default configuration for indexes when creating a collection

    > - `viewOn` (str): the name of the source collection or view from which to create the view

    > - `pipeline` (list): a list of aggregation pipeline stages

    > - `comment` (str): a user-provided comment to attach to this command. This option is only supported on MongoDB >= 4.4.

    > - `encryptedFields` (dict): (BETA) Document that describes the encrypted fields for Queryable Encryption. For example:

    >       {
    >         "escCollection": "enxcol_.encryptedCollection.esc",
    >         "ecocCollection": "enxcol_.encryptedCollection.ecoc",
    >         "fields": [
    >             {
    >                 "path": "firstName",
    >                 "keyId": Binary.from_uuid(UUID('00000000-0000-0000-0000-000000000000')),
    >                 "bsonType": "string",
    >                 "queries": {"queryType": "equality"}
    >             },
    >             {
    >                 "path": "ssn",
    >                 "keyId": Binary.from_uuid(UUID('04104104-1041-0410-4104-104104104104')),
    >                 "bsonType": "string"
    >             }
    >           ]
    >       }

    > - `clusteredIndex` (dict): Document that specifies the clustered index configuration. It must have the following form:

    >       {
    >           // key pattern must be {_id: 1}
    >           key: <key pattern>, // required
    >           unique: <bool>, // required, must be `true`
    >           name: <string>, // optional, otherwise automatically generated
    >           v: <int>, // optional, must be `2` if provided
    >       }

    > - `changeStreamPreAndPostImages` (dict): a document with a boolean field `enabled` for enabling pre- and post-images.

    Changed in version 4.2: Added the `check_exists`, `clusteredIndex`, and `encryptedFields` parameters.

    Changed in version 3.11: This method is now supported inside multi-document transactions with MongoDB 4.4+.

    Changed in version 3.6: Added `session` parameter.

    Changed in version 3.4: Added the collation option.

    Changed in version 3.0: Added the codec_options, read_preference, and write_concern options.

  cursor_command(command, value=1, read_preference=None, codec_options=None, session=None, comment=None, max_await_time_ms=None, **kwargs)

    Issue a MongoDB command and parse the response as a cursor.

    If the response from the server does not include a cursor field, an error will be thrown.

    Otherwise, behaves identically to issuing a normal MongoDB command.

    Parameters:

      - command (Union[str, MutableMapping[str, Any]]) –

        document representing the command to be issued, or the name of the command (for simple commands only).

        Note

        the order of keys in the command document is significant (the “verb” must come first), so commands which require multiple keys (e.g. findandmodify) should use an instance of `SON` or a string and kwargs instead of a Python dict.

      - value (Any) – value to use for the command verb when command is passed as a string

      - read_preference (Optional[_ServerMode]) – The read preference for this operation. See `read_preferences` for options. If the provided session is in a transaction, defaults to the read preference configured for the transaction. Otherwise, defaults to `PRIMARY`.

      - codec_options (Optional[CodecOptions[_CodecDocumentType]]) – A `CodecOptions` instance.

      - session (Optional[ClientSession]) – A `ClientSession`.

      - comment (Optional[Any]) – A user-provided comment to attach to future getMores for this command.

      - max_await_time_ms (Optional[int]) – The number of ms to wait for more data on future getMores for this command.

      - kwargs (Any) – additional keyword arguments will be added to the command document before it is sent

    Return type:

      CommandCursor[_DocumentType]

    Note

    `command()` does not obey this Database’s `read_preference` or `codec_options`. You must use the `read_preference` and `codec_options` parameters instead.

    Note

    `command()` does not apply any custom TypeDecoders when decoding the command response.

    Note

    If this client has been configured to use MongoDB Stable API (see versioned API), then `command()` will automatically add API versioning options to the given command. Explicitly adding API versioning options in the command and declaring an API version on the client is not supported.

    See also

    The MongoDB documentation on commands.

  dereference(dbref, session=None, comment=None, **kwargs)

    Dereference a `DBRef`, getting the document it points to.

    Raises `TypeError` if dbref is not an instance of `DBRef`. Returns a document, or `None` if the reference does not point to a valid document. Raises `ValueError` if dbref has a database specified that is different from the current database.

    Parameters:

      - dbref (DBRef) – the reference

      - session (Optional[ClientSession]) – a `ClientSession`.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

      - kwargs (Any) – any additional keyword arguments are the same as the arguments to `find()`.

    Return type:

      Optional[_DocumentType]

    Changed in version 4.1: Added `comment` parameter.

    Changed in version 3.6: Added `session` parameter.

  drop_collection(name_or_collection, session=None, comment=None, encrypted_fields=None)

    Drop a collection.

    Parameters:

      - name_or_collection (Union[str, Collection[_DocumentTypeArg]]) – the name of a collection to drop or the collection object itself

      - session (Optional[ClientSession]) – a `ClientSession`.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

      - encrypted_fields (Optional[Mapping[str, Any]]) –

        (BETA) Document that describes the encrypted fields for Queryable Encryption. For example:

            {
              "escCollection": "enxcol_.encryptedCollection.esc",
              "ecocCollection": "enxcol_.encryptedCollection.ecoc",
              "fields": [
                  {
                      "path": "firstName",
                      "keyId": Binary.from_uuid(UUID('00000000-0000-0000-0000-000000000000')),
                      "bsonType": "string",
                      "queries": {"queryType": "equality"}
                  },
                  {
                      "path": "ssn",
                      "keyId": Binary.from_uuid(UUID('04104104-1041-0410-4104-104104104104')),
                      "bsonType": "string"
                  }
              ]

            }

    Return type:

      dict[str, Any]

    Note

    The `write_concern` of this database is automatically applied to this operation.

    Changed in version 4.2: Added `encrypted_fields` parameter.

    Changed in version 4.1: Added `comment` parameter.

    Changed in version 3.6: Added `session` parameter.

    Changed in version 3.4: Apply this database’s write concern automatically to this operation when connected to MongoDB >= 3.4.

  get_collection(name, codec_options=None, read_preference=None, write_concern=None, read_concern=None)

    Get a `Collection` with the given name and options.

    Useful for creating a `Collection` with different codec options, read preference, and/or write concern from this `Database`.

        >>> db.read_preference
        Primary()
        >>> coll1 = db.test
        >>> coll1.read_preference
        Primary()
        >>> from pymongo import ReadPreference
        >>> coll2 = db.get_collection(
        ...     'test', read_preference=ReadPreference.SECONDARY)
        >>> coll2.read_preference
        Secondary(tag_sets=None)

    Parameters:

      - name (str) – The name of the collection - a string.

      - codec_options (Optional[CodecOptions[_DocumentTypeArg]]) – An instance of `CodecOptions`. If `None` (the default) the `codec_options` of this `Database` is used.

      - read_preference (Optional[_ServerMode]) – The read preference to use. If `None` (the default) the `read_preference` of this `Database` is used. See `read_preferences` for options.

      - write_concern (Optional[WriteConcern]) – An instance of `WriteConcern`. If `None` (the default) the `write_concern` of this `Database` is used.

      - read_concern (Optional[ReadConcern]) – An instance of `ReadConcern`. If `None` (the default) the `read_concern` of this `Database` is used.

    Return type:

      Collection[_DocumentType]

  list_collection_names(session=None, filter=None, comment=None, **kwargs)

    Get a list of all the collection names in this database.

    For example, to list all non-system collections:

        filter = {"name": {"$regex": r"^(?!system\.)"}}
        db.list_collection_names(filter=filter)

    Parameters:

      - session (Optional[ClientSession]) – a `ClientSession`.

      - filter (Optional[Mapping[str, Any]]) – A query document to filter the list of collections returned from the listCollections command.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

      - kwargs (Any) – Optional parameters of the listCollections command can be passed as keyword arguments to this method. The supported options differ by server version.

    Return type:

      list[str]

    Changed in version 3.8: Added the `filter` and `**kwargs` parameters.

    Added in version 3.6.

  list_collections(session=None, filter=None, comment=None, **kwargs)

    Get a cursor over the collections of this database.

    Cursors are closed automatically when they are exhausted (the last batch of data is retrieved from the database). If a cursor is not exhausted, it will be closed automatically upon garbage collection, which leaves resources open but unused for a potentially long period of time. To avoid this, best practice is to call `Cursor.close()` when the cursor is no longer needed, or use the cursor in a with statement:

        with database.list_collections() as cursor:
            for collection in cursor:
                print(collection)

    Parameters:

      - session (Optional[ClientSession]) – a `ClientSession`.

      - filter (Optional[Mapping[str, Any]]) – A query document to filter the list of collections returned from the listCollections command.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

      - kwargs (Any) –

        Optional parameters of the listCollections command can be passed as keyword arguments to this method. The supported options differ by server version.

    Returns:

      An instance of `CommandCursor`.

    Return type:

      CommandCursor[MutableMapping[str, Any]]

    Added in version 3.6.

  property name: str

    The name of this `Database`.

  validate_collection(name_or_collection, scandata=False, full=False, session=None, background=None, comment=None)

    Validate a collection.

    Returns a dict of validation info. Raises CollectionInvalid if validation fails.

    See also the MongoDB documentation on the validate command.

    Parameters:

      - name_or_collection (Union[str, Collection[_DocumentTypeArg]]) – A Collection object or the name of a collection to validate.

      - scandata (bool) – Do extra checks beyond checking the overall structure of the collection.

      - full (bool) – Have the server do a more thorough scan of the collection. Use with scandata for a thorough scan of the structure of the collection and the individual documents.

      - session (Optional[ClientSession]) – a `ClientSession`.

      - background (Optional[bool]) – A boolean flag that determines whether the command runs in the background. Requires MongoDB 4.4+.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

    Return type:

      dict[str, Any]

    Changed in version 4.1: Added `comment` parameter.

    Changed in version 3.11: Added `background` parameter.

    Changed in version 3.6: Added `session` parameter.

  watch(pipeline=None, full_document=None, resume_after=None, max_await_time_ms=None, batch_size=None, collation=None, start_at_operation_time=None, session=None, start_after=None, comment=None, full_document_before_change=None, show_expanded_events=None)

    Watch changes on this database.

    Performs an aggregation with an implicit initial `$changeStream` stage and returns a `DatabaseChangeStream` cursor which iterates over changes on all collections in this database.

    Introduced in MongoDB 4.0.

        with db.watch() as stream:
            for change in stream:
                print(change)

    The `DatabaseChangeStream` iterable blocks until the next change document is returned or an error is raised. If the `next()` method encounters a network error when retrieving a batch from the server, it will automatically attempt to recreate the cursor such that no change events are missed. Any error encountered during the resume attempt indicates there may be an outage and will be raised.

        try:
            with db.watch([{"$match": {"operationType": "insert"}}]) as stream:
                for insert_change in stream:
                    print(insert_change)
        except pymongo.errors.PyMongoError:
            # The ChangeStream encountered an unrecoverable error or the
            # resume attempt failed to recreate the cursor.
            logging.error("...")

    For a precise description of the resume process see the change streams specification.

    Parameters:

      - pipeline (Optional[_Pipeline]) – A list of aggregation pipeline stages to append to an initial `$changeStream` stage. Not all pipeline stages are valid after a `$changeStream` stage, see the MongoDB documentation on change streams for the supported stages.

      - full_document (Optional[str]) – The fullDocument to pass as an option to the `$changeStream` stage. Allowed values: ‘updateLookup’, ‘whenAvailable’, ‘required’. When set to ‘updateLookup’, the change notification for partial updates will include both a delta describing the changes to the document, as well as a copy of the entire document that was changed from some time after the change occurred.

      - full_document_before_change (Optional[str]) – Allowed values: ‘whenAvailable’ and ‘required’. Change events may now result in a ‘fullDocumentBeforeChange’ response field.

      - resume_after (Optional[Mapping[str, Any]]) – A resume token. If provided, the change stream will start returning changes that occur directly after the operation specified in the resume token. A resume token is the _id value of a change document.

      - max_await_time_ms (Optional[int]) – The maximum time in milliseconds for the server to wait for changes before responding to a getMore operation.

      - batch_size (Optional[int]) – The maximum number of documents to return per batch.

      - collation (Optional[_CollationIn]) – The `Collation` to use for the aggregation.

      - start_at_operation_time (Optional[Timestamp]) – If provided, the resulting change stream will only return changes that occurred at or after the specified `Timestamp`. Requires MongoDB >= 4.0.

      - session (Optional[ClientSession]) – a `ClientSession`.

      - start_after (Optional[Mapping[str, Any]]) – The same as resume_after except that start_after can resume notifications after an invalidate event. This option and resume_after are mutually exclusive.

      - comment (Optional[Any]) – A user-provided comment to attach to this command.

      - show_expanded_events (Optional[bool]) – Include expanded events such as DDL events like dropIndexes.

    Returns:

      A `DatabaseChangeStream` cursor.

    Return type:

      DatabaseChangeStream[_DocumentType]

    Changed in version 4.3: Added show_expanded_events parameter.

    Changed in version 4.2: Added `full_document_before_change` parameter.

    Changed in version 4.1: Added `comment` parameter.

    Changed in version 3.9: Added the `start_after` parameter.

    Added in version 3.7.

    See also

    The MongoDB documentation on changeStreams.

  with_options(codec_options: None = None, read_preference: _ServerMode | None = None, write_concern: WriteConcern | None = None, read_concern: ReadConcern | None = None) → Database[_DocumentType]
  with_options(codec_options: bson.CodecOptions[_DocumentTypeArg], read_preference: _ServerMode | None = None, write_concern: WriteConcern | None = None, read_concern: ReadConcern | None = None) → Database[_DocumentTypeArg]

    Get a clone of this database changing the specified settings.

        >>> db1.read_preference
        Primary()
        >>> from pymongo.read_preferences import Secondary
        >>> db2 = db1.with_options(read_preference=Secondary([{'node': 'analytics'}]))
        >>> db1.read_preference
        Primary()
        >>> db2.read_preference
        Secondary(tag_sets=[{'node': 'analytics'}], max_staleness=-1, hedge=None)

    Parameters:

      - codec_options – An instance of `CodecOptions`. If `None` (the default) the `codec_options` of this `Collection` is used.

      - read_preference – The read preference to use. If `None` (the default) the `read_preference` of this `Collection` is used. See `read_preferences` for options.

      - write_concern – An instance of `WriteConcern`. If `None` (the default) the `write_concern` of this `Collection` is used.

      - read_concern – An instance of `ReadConcern`. If `None` (the default) the `read_concern` of this `Collection` is used.

    Added in version 3.8.