1. MongoEngine
NoORM for NoSQL
Serge Matveenko
github.com/lig
PyCon Russia 2013

2. Quick MongoDB intro
NoSQL document-oriented database
● scalable (auto-sharding, replication)
● high-performance (~104-105 queries/sec)
● open source (db: AGPL, drivers: Apache)

3. RDBMS vs MongoDB
RDBMS MongoDB
data DB + Driver DB + PyMongo
aggregation
constraints Application
validation
cascade updates
business logic Application

4. RDBMS vs MongoDB
RDBMS MongoDB
data DB + Driver DB + PyMongo
aggregation
constraints MongoEngine
validation
cascade updates
business logic Application Application

5. How it looks
MongoEngine class CharacterName(EmbeddedDocument):
first = StringField()
last = StringField()
class Character(Document):
name = EmbeddedDocumentField(CharacterName)
rating = IntField()
MongoDB {
"_id" : ObjectId
("5125e0ee98764119e77d9b1f"),
"_types" : ["Character"],
"rating" : 42,
"name" : {"_types" : ["CharacterName"],
"last": "Connor", "_cls": "CharacterName",
"first": "Sarah"},
"_cls": "Character"
}

6. How it looks
(MongoEngine 0.8)
MongoEngine class CharacterName(EmbeddedDocument):
first = StringField()
last = StringField()
class Character(Document):
name = EmbeddedDocumentField(CharacterName)
rating = IntField()
MongoDB {
"_id" : ObjectId
("5125e0ee98764119e77d9b1f"),
"rating" : 42,
"name" : {"last": "Connor",
"_cls": "CharacterName", "first": "Sarah"},
"_cls": "Character"
}

7. Querying with MongoEngine
Simple
db.character.find({'name.first': 'John'})
Character.objects(name__first='John')
db.character.find({rating: {$gte: 42}}).limit(5)
Character.objects(rating__gte=42)[:5]
db.character.find({rating: {$exists: false}})
Character.objects(rating__exists=False)

8. Querying with MongoEngine
Map/Reduce
db.character.mapReduce(map_f, reduce_f, {out: 'mr_col'});
db.mr_col.find();
Character.objects.map_reduce(map_f, reduce_f, 'mr_col')

9. Updating with MongoEngine
Creating
db.character.save(
{name: {first: 'John', last: 'Conor'}, rating: 42})
jc = Character(
name=CharacterName(first='John', last='Conor'),
rating=42)
jc.save()

10. Updating with MongoEngine
Atomic updates
db.character.update(
{name: {first: "John", last: "Conor"}},
{$set: {"name.last": "Connor"}})
Character.objects(
name=CharacterName(first='John', last='Conor')
).update(set__name__last='Connor')

11. Under the hood
"C" BSON
MongoDB PyMongo MongoEngine
Module
s es
pe ass
data tiv e ty e cl
Bina
ry na ativ
yt hon De clar
P
JavaScript
Console

12. Under the hood
"C" BSON
MongoDB PyMongo MongoEngine
Module
s es
pe ass
data tiv e ty e cl
Bina
ry na ativ
yt hon De clar
P
JavaScript
Console

13. Performance

14. Django integration
Out of the box
● authentication backend
● session engine
● GridFSStorage
Third party
● stephrdev/django-mongoforms (Model Forms port)
● wpjunior/django-mongotools (forms, generic views)
● lig/django-registration-me (django-registration port)

15. Customizing things
(added today. sorry:)
● SequenceField(value_decorator=func)
● StringField(regex=r'…')
● URLField(verify_exists=True)
● …
● Inherit from standard Field classes
● Write your own Field classes
● Inherit from BaseDocument class,
don't forget metaclass!
● Any metamagic your like…

16. Questions?
Serge Matveenko (github.com/lig)
mongoengine.org
www.mongodb.org
Thanks to
Ross Lawley (github.com/rozza)
Elena Voronina :)