=================
- EnumField improvements: now ``choices`` limits the values of an enum to allow
- Fix bug that prevented instance queryset from using custom queryset_class 2589
- Fix deepcopy of EmbeddedDocument 2202
- Introduce a base exception class for MongoEngine exceptions (MongoEngineException).
Note that this doesn't concern the pymongo errors 2515
- Fix error when using precision=0 with DecimalField 2535
- Add support for regex and whole word text search query 2568
- Add support for update aggregation pipeline 2578
- BREAKING CHANGE: Updates to support pymongo 4.0. Where possible deprecated
functionality has been migrated, but additional care should be taken when
migrating to pymongo 4.0 as existing code may have been using deprecated
features which have now been removed 2614.
For the pymongo migration guide see:
https://pymongo.readthedocs.io/en/stable/migrate-to-pymongo4.html.
In addition to the changes in the migration guide, the following is a high
level overview of the changes made to MongoEngine when using pymongo 4.0:
- limited support of geohaystack indexes has been removed
- ``QuerySet.map_reduce`` has been migrated from ``Collection.map_reduce``
and ``Collection.inline_map_reduce`` to use
``db.command({mapReduce: ..., ...})`` and support between the two may need
additional verification.
- UUIDs are encoded with the ``pythonLegacy`` encoding by default instead of
the newer and cross platform ``standard`` encoding. Existing UUIDs will
need to be migrated before changing the encoding, and this should be done
explicitly by the user rather than switching to a new default by
MongoEngine. This default will change at a later date, but to allow
specifying and then migrating to the new format a default ``json_options``
has been provided.
- ``Queryset.count`` has been using ``Collection.count_documents`` and
transparently falling back to ``Collection.count`` when using features that
are not supported by ``Collection.count_documents``. ``Collection.count``
has been removed and no automatic fallback is possible. The migration guide
documents the extended functionality which is no longer supported. Rewrite
the unsupported queries or fetch the whole result set and perform the count
locally.
- Pymongo 4 removed db.authenticate(), on which we were relying for authenticating
with username/password. The migration involved switching to providing credentials to
MongoClient BUT in case the authSource isn't provided, db.authenticate used to default to
authSource=current-database and MongoClient defaults to authSource="admin". Long story short,
if you observe authentication issue after migrating, make sure you provide the authSource
explicitly. (see 2626)