Class query_counter

mongoengine/context_managers.py:193–288

Query_counter context manager to get the number of queries. This works by updating the `profiling_level` of the database so that all queries get logged, resetting the db.system.profile collection at the beginning of the context and counting the new entries. This was designed for debuggi

class query_counter:
    """Query_counter context manager to get the number of queries.
    This works by updating the `profiling_level` of the database so that all queries get logged,
    resetting the db.system.profile collection at the beginning of the context and counting the new entries.

    This was designed for debugging purpose. In fact it is a global counter so queries issued by other threads/processes
    can interfere with it

    Usage:

    .. code-block:: python

        class User(Document):
            name = StringField()

        with query_counter() as q:
            user = User(name='Bob')
            assert q == 0       # no query fired yet
            user.save()
            assert q == 1       # 1 query was fired, an 'insert'
            user_bis = User.objects().first()
            assert q == 2       # a 2nd query was fired, a 'find_one'

    Be aware that:

    - Iterating over large amount of documents (>101) makes pymongo issue `getmore` queries to fetch the next batch of documents (https://www.mongodb.com/docs/manual/tutorial/iterate-a-cursor/#cursor-batches)
    - Some queries are ignored by default by the counter (killcursors, db.system.indexes)
    """

    def __init__(self, alias=DEFAULT_CONNECTION_NAME):
        self.db = get_db(alias=alias)
        self.initial_profiling_level = None
        self._ctx_query_counter = 0  # number of queries issued by the context

        self._ignored_query = {
            "ns": {"$ne": "%s.system.indexes" % self.db.name},
            "op": {"$ne": "killcursors"},  # MONGODB < 3.2
            "command.killCursors": {"$exists": False},  # MONGODB >= 3.2
        }

    def _turn_on_profiling(self):
        profile_update_res = self.db.command({"profile": 0})
        self.initial_profiling_level = profile_update_res["was"]

        self.db.system.profile.drop()
        self.db.command({"profile": 2})

    def _resets_profiling(self):
        self.db.command({"profile": self.initial_profiling_level})

    def __enter__(self):
        self._turn_on_profiling()
        return self

    def __exit__(self, t, value, traceback):
        self._resets_profiling()

    def __eq__(self, value):