mongoschema

Super lightweight python MongoDB ORM built on top of pymongo using raw python types

NOTICE

This is still very young and immature code. I am using it in production for a few simple and low-traffic applications right now and still find myself fixing some pretty critical bugs every once in a while.

If you're interested in giving it a go but not sure if it's worth the risk, get in touch with me and we'll figure it out.

Support

Currently only tested with python 2.7. No idea if it works with anything else, but I would say there's a good chance.

Installation

pip install git+git://github.com/hershaw/mongoschema.git@master#egg=mongoschema

Update

pip install git+git://github.com/hershaw/mongoschema.git@master#egg=mongoschema --upgrade

Usage

Step 1: Define the schema

To do this, you need to import the MongoSchema and MongoField classes:

from mongoschema import MongoSchema, MongoField as MF

Subclassing MongoSchema and adding a few attributes to it is how you define a collection. For example, here is a User schema with only the required fields:

conn = pymongo.MongoClient()
db = conn['myapp']

class User(MongoSchema):
    collection = db.user
    schema = {
        'username': MF(unicode),
    }

Two things to note right away:

• An id field is automatically added and maps to _id in the collection.
• Note that you are responsible for importing your own pymongo DB connection.

So now that you have a collection defined for a user, let's create one and access the data:

user = User.create(username=u'Billy')
print(user.username) # "Billy"

And that's it, the user is created and saved to the database. Now let's use a few more features:

class User(MongoSchema):
    collection = db.user
    schema = {
        'username': MF(unicode),
        'email': MF(unicode, validate_regexp=re.compile('[^@]+@[^@]+\.[^@]+')),
        'password': MF(unicode),
        'salt': MF(unicode),
    }
    indexes = [
      'username',
      ['email', {'unique': True}],
    ]
    
    @staticmethod
    def register(username, email, password):
      hashed_password = salt_password(password, unicode(uuid.uuid4().hex))
      user = User.create(
        username=username,
        email=email,
        password=hashed_password,
        salt=salt
      )
      return user

Three new things here:

• We have added a new field email that has a validation regexp that it must pass before being saved to the collection.
• We have added an index on the field username and a unique index on the email field.
• We now have a static method that we can use as a wrapper for the default create function that we used directly earlier.

Indexes

The indexes attribute is a list. Each element of the list will be passed on as arguments to pymongo's ensure_index function. Each index can be in two distinct forms:

• A single string. This is the simplest and the pymongo ensure_index is called with that string.
• A list. In this form, the first element passed as the first argument to ensure_index while the rest are passed as kwargs.

All of the following forms are acceptable entries into the indexes array:

'email' # simplest
['email', {}] # functionally equivilent to the above
[(('email', -1),), {'sparse': True}], # descending sparse index
[(('username', -1), ('email', -1)), {}] # compound index

Static functions on MongoSchema classes

You will never instiantiate anything that subclasses the MongoSchema class. You will define functions using the staticmethod and classmethod decorators. These classes are for defining structure, actually dealing with data is for another type of class.

Speaking of...

Step 2: Define the doc classes

When you defined the User class and used it to create a user, notice that the instance that was returned from create was NOT an instance of User.

print(user) # -> "<class 'base.MongoDoc'>"

The MongoDoc base class does provide simple functionality like save, update, and remove but nothing else. If you need to add instance methods to your users, you need to subclass MongoDoc and set the result as the User's doc_class.

from mongoschema import MongoDoc

class UserDoc(MongoDoc):
  
  def pretty_print(self):
    print('%s - %s' % self.email, self.username)


class User(MongoDoc):
  collection = db.user
  # Schema and indexes and stuff...
  doc_class = UserDoc
  
user = Use.create(username='sam', email='[email protected]')
print(type(user)) # "<class '__main__.UserDoc'>"
print(user.pretty_print()) # "[email protected] - sam"