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Differences between Mongomallard and Mongoengine

  • All document fields are lazily evaluated, resulting in much faster object initialization time.
  • _data is removed due to lazy evaluation. to_dict() can be used to convert a document to a dictionary, and _internal_data contains previously evaluated data.
  • Field methods to_python, from_python, to_mongo, value_for_instance:
    • to_python is called when converting from a MongoDB type to a document Python type only.
    • from_python is called when converting an assignment in Python to the document Python type.
    • to_mongo is called when converting from a document Python type to a MongoDB type.
    • value_for_instance is called just before returning a value in Python allowing for instance-specific transformations.
  • pre_init, post_init, pre_save_post_validation signals are removed to ensure fast object initialization.
  • DecimalField is removed since there is no corresponding MongoDB type
  • LongField is removed since it is equivalent with IntField
  • Adding SafeReferenceField which returns None if the reference does not exist.
  • Adding SafeReferenceListField which doesn't return references that don't exist.
  • Accessing a ListField(ReferenceField) doesn't automatically dereference all objects since they are lazily evaluated. A SafeReferenceListField may be used instead.
  • Accessing a related object's id doesn't fetch the object from the database, e.g. where author is a ReferenceField will not make a database lookup except when using a SafeReferenceField. When inheritance is allowed, a proxy object will be returned, otherwise a lazy object from the referenced document class will be returned.
  • The primary key is only stored as _id in the database and is referenced in Python as pk or as the name of the primary key field.
  • Saves are not cascaded by default.
  • supports full=True keyword argument to force saving all model fields.
  • _get_changed_fields() / _changed_fields returns a set of field names (not db field names)
  • Simplified EmailField email regex to be more compatible
  • Assigning invalid types (e.g. an invalid string to IntField) raises immediately a ValueError
  • order_by() without an argument resets the ordering (no ordering will be applied)

Untested / not implemented yet:

  • Dynamic documents / DynamicField, dynamic addition/deletion of fields
  • Field display name methods
  • SequenceField
  • Pickling documents
  • FileField
  • All Geo fields
  • no_dereference()
  • using SafeReferenceListField with GenericReferenceField
  • max_depth argument for doc.reload()
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