Django settings configure databases with two engines

Question

I'm trying to run DJango with postgresql and postgis

for Django & postgresql I configures the setting.py file as follows

DATABASES = {
    'default': {
        'ENGINE':'django.db.backends.postgresql_psycopg2',
        'NAME': 'myDatabaseName',
        'USER': 'postgres',
        'PASSWORD': 'MyPassword',
        'HOST': '',
        'PORT': '5432',
    }
}

but looking at the tutorial of Django geo example shows to use this

DATABASES = {
    'default': {
         'ENGINE': 'django.contrib.gis.db.backends.postgis',
         'NAME': 'geodjango',
         'USER': 'geo',
     }
}

The Problem: I need both engines to work on the same database as I'm using postgresql with the postgis extension and I'd like to define a table with a geographic column like this:

MapLocation GEOGRAPHY(POINT)

and refer to it from Django like this maplocation = models.PointField()

obviously i need a mash of both engines with the rest as mentioned above in 'default' I just don't know how to make it work

Answer 1

In Django, you may define multiple database connections:

DATABASES = {
    'default': {
        'NAME': 'app_data',
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'USER': 'postgres_user',
        'PASSWORD': 's3krit'
    },
    'users': {
        'NAME': 'user_data',
        'ENGINE': 'django.db.backends.mysql',
        'USER': 'mysql_user',
        'PASSWORD': 'priv4te'
    }
}

Reference: https://docs.djangoproject.com/en/dev/topics/db/multi-db/#defining-your-databases

Answer 2

I maybe a bit late, but if anyone else stumbles upon this link, here's how i did it:

in your settings.py

DATABASES = {
'default': {
    'NAME': 'app_data',
    'ENGINE': 'django.db.backends.postgresql_psycopg2',
    'USER': 'postgres_user',
    'PASSWORD': 's3krit'
},
'location': {
    'NAME': 'app_data',
    'ENGINE': 'django.contrib.gis.db.backends.postgis',,
    'USER': 'postgres_user',
    'PASSWORD': 's3krit'
}

}

So we only changed the engine in settings.

Now, we need to tell the database to write and read geography data from the second database.

For that, in your models.py, lets say you have a Location class:

class Location(models.Model):
location_points = models.PointField(default=Point(0,0))
address = models.TextField(null=True,blank=True)
label = models.CharField(max_length=200,null=True,blank=True)

class Meta:
    db_table = 'location'

Note the db_table attribute in the Meta class, this is necessary.

Now you need to define database router to use the 'location' database whenever the db_table is 'location'.

Here's how the router class should look like:

class DbRouter(object):
"""
A router to control all database operations on models in the
auth application.
"""
def db_for_read(self, model, **hints):
    """
    Attempts to read location models go to location database.
    """
    if model._meta.db_table == 'location':
        return 'location'
    return 'default'

def db_for_write(self, model, **hints):
    """
    Attempts to write location models go to the location database.
    """
    if model._meta.db_table == 'location':
        return 'location'
    return 'default'


def allow_relation(self, obj1, obj2, **hints):
    """
    allow relations involving the location database
    """
    return True

You are now good to go, save the router class in a file named dbrouter.py inside your app.

And in your settings.py file, add this:

DATABASE_ROUTERS = ['app_name.dbrouters.DbRouter', ]