Classe « MongoClient »

Méthode pymongo.MongoClient.watch

Signature de la méthode watch

def watch(self, 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) 

Description

watch.__doc__

Watch changes on this cluster.

        Performs an aggregation with an implicit initial ``$changeStream``
        stage and returns a
        :class:`~pymongo.change_stream.ClusterChangeStream` cursor which
        iterates over changes on all databases on this cluster.

        Introduced in MongoDB 4.0.

        .. code-block:: python

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

        The :class:`~pymongo.change_stream.ClusterChangeStream` iterable
        blocks until the next change document is returned or an error is
        raised. If the
        :meth:`~pymongo.change_stream.ClusterChangeStream.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.

        .. code-block:: python

            try:
                with client.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): 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): The fullDocument to pass as an option
            to the ``$changeStream`` stage. Allowed values: 'updateLookup'.
            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.
          - `resume_after` (optional): 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): The maximum time in milliseconds
            for the server to wait for changes before responding to a getMore
            operation.
          - `batch_size` (optional): The maximum number of documents to return
            per batch.
          - `collation` (optional): The :class:`~pymongo.collation.Collation`
            to use for the aggregation.
          - `start_at_operation_time` (optional): If provided, the resulting
            change stream will only return changes that occurred at or after
            the specified :class:`~bson.timestamp.Timestamp`. Requires
            MongoDB >= 4.0.
          - `session` (optional): a
            :class:`~pymongo.client_session.ClientSession`.
          - `start_after` (optional): The same as `resume_after` except that
            `start_after` can resume notifications after an invalidate event.
            This option and `resume_after` are mutually exclusive.

        :Returns:
          A :class:`~pymongo.change_stream.ClusterChangeStream` cursor.

        .. versionchanged:: 3.9
           Added the ``start_after`` parameter.

        .. versionadded:: 3.7

        .. mongodoc:: changeStreams

        .. _change streams specification:
            https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst