103 lines
3.4 KiB
ReStructuredText
103 lines
3.4 KiB
ReStructuredText
.. _guide-connecting:
|
|
|
|
=====================
|
|
Connecting to MongoDB
|
|
=====================
|
|
|
|
To connect to a running instance of :program:`mongod`, use the
|
|
:func:`~mongoengine.connect` function. The first argument is the name of the
|
|
database to connect to::
|
|
|
|
from mongoengine import connect
|
|
connect('project1')
|
|
|
|
By default, MongoEngine assumes that the :program:`mongod` instance is running
|
|
on **localhost** on port **27017**. If MongoDB is running elsewhere, you should
|
|
provide the :attr:`host` and :attr:`port` arguments to
|
|
:func:`~mongoengine.connect`::
|
|
|
|
connect('project1', host='192.168.1.35', port=12345)
|
|
|
|
If the database requires authentication, :attr:`username` and :attr:`password`
|
|
arguments should be provided::
|
|
|
|
connect('project1', username='webapp', password='pwd123')
|
|
|
|
Uri style connections are also supported - just supply the uri as
|
|
the :attr:`host` to
|
|
:func:`~mongoengine.connect`::
|
|
|
|
connect('project1', host='mongodb://localhost/database_name')
|
|
|
|
Note that database name from uri has priority over name
|
|
in ::func:`~mongoengine.connect`
|
|
|
|
ReplicaSets
|
|
===========
|
|
|
|
MongoEngine supports :class:`~pymongo.mongo_replica_set_client.MongoReplicaSetClient`
|
|
to use them please use a URI style connection and provide the `replicaSet` name in the
|
|
connection kwargs.
|
|
|
|
Read preferences are supported through the connection or via individual
|
|
queries by passing the read_preference ::
|
|
|
|
Bar.objects().read_preference(ReadPreference.PRIMARY)
|
|
Bar.objects(read_preference=ReadPreference.PRIMARY)
|
|
|
|
Multiple Databases
|
|
==================
|
|
|
|
Multiple database support was added in MongoEngine 0.6. To use multiple
|
|
databases you can use :func:`~mongoengine.connect` and provide an `alias` name
|
|
for the connection - if no `alias` is provided then "default" is used.
|
|
|
|
In the background this uses :func:`~mongoengine.register_connection` to
|
|
store the data and you can register all aliases up front if required.
|
|
|
|
Individual documents can also support multiple databases by providing a
|
|
`db_alias` in their meta data. This allows :class:`~pymongo.dbref.DBRef` objects
|
|
to point across databases and collections. Below is an example schema, using
|
|
3 different databases to store data::
|
|
|
|
class User(Document):
|
|
name = StringField()
|
|
|
|
meta = {"db_alias": "user-db"}
|
|
|
|
class Book(Document):
|
|
name = StringField()
|
|
|
|
meta = {"db_alias": "book-db"}
|
|
|
|
class AuthorBooks(Document):
|
|
author = ReferenceField(User)
|
|
book = ReferenceField(Book)
|
|
|
|
meta = {"db_alias": "users-books-db"}
|
|
|
|
|
|
Switch Database Context Manager
|
|
===============================
|
|
|
|
Sometimes you may want to switch the database to query against for a class
|
|
for example, archiving older data into a separate database for performance
|
|
reasons.
|
|
|
|
The :class:`~mongoengine.context_managers.switch_db` context manager allows
|
|
you to change the database alias for a given class allowing quick and easy
|
|
access to the same User document across databases::
|
|
|
|
from mongoengine.context_managers import switch_db
|
|
|
|
class User(Document):
|
|
name = StringField()
|
|
|
|
meta = {"db_alias": "user-db"}
|
|
|
|
with switch_db(User, 'archive-user-db') as User:
|
|
User(name="Ross").save() # Saves the 'archive-user-db'
|
|
|
|
.. note:: Make sure any aliases have been registered with
|
|
:func:`~mongoengine.register_connection` before using the context manager.
|