On Jul 13, 4:51 pm, Emily Rodgers <emily.kate.rodg...@googlemail.com>
wrote:
> On Jul 3, 6:36 pm, Emily Rodgers <emily.kate.rodg...@googlemail.com>
> wrote:
>
>
>
> > 2009/7/3 Alex Gaynor <alex.gay...@gmail.com>:
>
> > > On Fri, Jul 3, 2009 at 12:25 PM, Emily Rodgers
> > > <emily.kate.rodg...@googlemail.com> wrote:
>
> > >> On Jul 3, 3:29 pm, Emily Rodgers <emily.kate.rodg...@googlemail.com>
> > >> wrote:
> > >> > On Jul 1, 3:44 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
>
> > >> > > On Wed, Jul 1, 2009 at 9:39 AM, Emily Rodgers <
>
> > >> > > emily.kate.rodg...@googlemail.com> wrote:
>
> > >> > > > On Jul 1, 3:22 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
> > >> > > > > On Wed, Jul 1, 2009 at 9:16 AM, Emily Rodgers <
>
> > >> > > > > emily.kate.rodg...@googlemail.com> wrote:
>
> > >> > > > > > On Jun 25, 6:45 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
> > >> > > > > > > On Thu, Jun 25, 2009 at 10:24 AM, Tim Chase
> > >> > > > > > > <django.us...@tim.thechases.com>wrote:
> > >> > > > > > > > > Right now, Django doesn't seem to support the multiple
> > >> > > > > > > > > databases on the same server or different servers. Will
> > >> > > > > > > > > that
> > >> > > > > > > > > feature be available out of the box for future releases?
>
> > >> > > > > > > > You may want to eavesdrop on the Django Developers group
> > >> > > > > > > > (as
> > >> > > > > > > > opposed to this Django Users group) where Alex Gaynor has
> > >> > > > > > > > been
> > >> > > > > > > > posting updates on his GSoC project to add multi-DB support
> > >> > > > > > > > to
> > >> > > > > > > > Django[1]. There are several aspects to multi-DB
> > >> > > > > > > > support[2]
> > >> > > > > > > > but
> > >> > > > > > > > I believe he's addressing some of the more common
> > >> > > > > > > > use-cases.
> > >> > > > > > > > You
> > >> > > > > > > > can even follow along if you like to live dangerously as I
> > >> > > > > > > > believe he's got a public repository for his code on
> > >> > > > > > > > GitHub.
>
> > >> > > > > > > > -tim
>
> > >> > > > > > > > [1]
>
> > >> > > > >http://groups.google.com/group/django-developers/search?group=django-.
> > >> > > > > > ..
>
> > >> > > > > > > > [2]
>
> > >> > > > >http://groups.google.com/group/django-users/browse_thread/thread/6630.
> > >> > > > > > ..
> > >> > > > > > > > for my posted concerns
>
> > >> > > > > > > I have both a public code repository on github at
> > >> > > > > > github.com/alex/django/ as
> > >> > > > > > > well as a branch in Django's SVN at branches/soc2009/multidb.
> > >> > > > > > > The
> > >> > > > best
> > >> > > > > > > place to find out about the work is the django-developers
> > >> > > > > > > list, where
> > >> > > > I
> > >> > > > > > have
> > >> > > > > > > sent any number of emails discussing both the overall design,
> > >> > > > > > > as well
> > >> > > > as
> > >> > > > > > the
> > >> > > > > > > status.
>
> > >> > > > > > > Alex
>
> > >> > > > > > > --
> > >> > > > > > > "I disapprove of what you say, but I will defend to the death
> > >> > > > > > > your
> > >> > > > right
> > >> > > > > > to
> > >> > > > > > > say it." --Voltaire
> > >> > > > > > > "The people's good is the highest law."--Cicero
>
> > >> > > > > > Hi,
>
> > >> > > > > > Alex - do you know roughly when this is likely to be
> > >> > > > > > incorporated into
> > >> > > > > > django? I am working on a project that is going to need to
> > >> > > > > > connect to
> > >> > > > > > multiple databases (I am just planning / designing at the
> > >> > > > > > moment), and
> > >> > > > > > I want to know whether I should start investigating how to do
> > >> > > > > > this
> > >> > > > > > using django 1.0.2 or if that would be a waste of my time.
>
> > >> > > > > > If it is going to be a while, where would you suggest I start
> > >> > > > > > looking
> > >> > > > > > if I need to understand how to do it with django 1.0.2?
>
> > >> > > > > > Cheers,
> > >> > > > > > Em
>
> > >> > > > > It will, at a minimum not occur until the end of the summer.
> > >> > > > > Beyond that
> > >> > > > I
> > >> > > > > can't make any really useful guesses, other than to say that the
> > >> > > > aggregation
> > >> > > > > GSOC project from last summer
> > >> > > > > ultimately made it's way into django trunk in January, about 3-4
> > >> > > > > months
> > >> > > > > after the official end of GSOC. That may or may not ultimately
> > >> > > > > be
> > >> > > > > representative of how long it will take multi-db to make it's way
> > >> > > > > back
> > >> > > > into
> > >> > > > > Django. A lot of it probably depends on how the 1.2/1.3 releases
> > >> > > > > are
> > >> > > > > scheduled. For example is 1.2 ends up being a smaller release
> > >> > > > > that's put
> > >> > > > > out in Novemberish I wouldn't expect multi-db to be considered
> > >> > > > > for
> > >> > > > > trunk
> > >> > > > > until 1.3. Like I said all of that's rather speculative :)
>
> > >> > > > > Alex
> > >> > > > > --
> > >> > > > > "I disapprove of what you say, but I will defend to the death
> > >> > > > > your
> > >> > > > > right
> > >> > > > to
> > >> > > > > say it." --Voltaire
> > >> > > > > "The people's good is the highest law."--Cicero
>
> > >> > > > Thanks Alex. I don't think I can wait that long so it looks like I
> > >> > > > am
> > >> > > > going to have to get my hands dirty!
>
> > >> > > > Is this [1] a sensible starting point?
>
> > >> > > > [1]
>
> > >> > > > >http://www.mechanicalgirl.com/view/multiple-database-connection-a-sim...
>
> > >> > > That blog post is a good source of information, as
> > >> > > is:http://www.eflorenzano.com/blog/post/easy-multi-database-support-djan...
> > >> > > unfortunately appears to be down right now).
>
> > >> > Hi,
>
> > >> > I have tried implementing this, but I am running into the problems
> > >> > that others have about too many idle MySQLconnections. Is there an
> > >> > easy way to get around this?
>
> > >> OK now I am running into even more problems :(
>
> > >> I am probably being dumb, but I assumed there were only problems with
> > >> foreign keys accross the different databases, but I am finding that I
> > >> can't follow foreign keys from the secondary database to another table
> > >> in the secondary database (even though both tables have the
> > >> MultiDbManager defined for them). It just assumes all foreign keys are
> > >> for tables in my primary database :(
>
> > >> I may have to set up another script on another django project with a
> > >> cli to get the data I want since I am only reading from the second db
> > >> (it just seems to wrong!!). Or maybe just use mysqldb?
>
> > > Does your multidbmanagerhave use_for_related_fields = True on it?
>
> > Ah - no. Thanks for spotting that!
>
> > <trying it out>
>
> > Yay - it worked. Thanks Alex :-)
>
> > Still stuck on the too manyconnectionsthing. Will have to look into
> > it on Monday though. Any ideas welcome.
>
> > Em
>
> I am still hitting a brick wall with this 'too-many-connections'
> thing :(
>
> I am assuming that I need to be doing something with the Manager
> creation_counter, but I can't see where this is being used to close
> default connections, so trying to implement something similar is
> tricky :(
>
> Can anyone help?
>
> Em
I finally think I have got this working! I have only tested this using
a script that pokes data into a database using django, not using a web
app (yet), so it may need tweaking in that situation (the signal
stuff), but, hopefully that won't be too much of a problem.
Basically I found an example that kimus.linuxus provided [1] that uses
a later version of django (I am using 1.0.2), and used the ideas from
it to adapt Eric Florenzano's example, and here is what I did:
In my models.py:
from project.app.managers import *
class Db1Model(models.Model):
_default_manager = MultiDBManager('db1')
objects = MultiDBManager('db1')
db = 'db1'
class Meta:
abstract = True
# then for all models that use db1:
class MyModelFromDb1(Db1Model):
...
class Db2Model(models.Model):
_default_manager = MultiDBManager('db2')
objects = MultiDBManager('db2')
db = 'db2'
class Meta:
abstract = True
# ditto for models in db2
class MyModelFromDb2(Db2Model):
...
Then in managers.py:
from django.db import models
from django.conf import settings
from django.db.models import sql
from django.db.transaction import savepoint_state
from django.core import signals
try:
import thread
except ImportError:
import dummy_thread as thread
_connections = {}
def close_connection(**kwargs):
global _connections
for connection in _connections.itervalues():
connection.close()
_connections = {}
signals.request_finished.connect(close_connection)
class MultiDBManager(models.Manager):
def __init__(self, database, *args, **kwargs):
self.database = database
self.use_for_related_fields = True
super(MultiDBManager, self).__init__(*args, **kwargs)
def get_query_set(self):
qs = super(MultiDBManager, self).get_query_set()
qs.query.connection = self.get_db_wrapper()
return qs
def get_db_wrapper(self):
if not self.database:
from django import connection
return connection
if not _connections.has_key(self.database):
settings_dict = settings.DATABASES[self.database]
backend = __import__('django.db.backends.%s.base' %
settings_dict['DATABASE_ENGINE'], {}, {}, ['base'])
backup = {}
for key, value in settings_dict.iteritems():
backup[key] = getattr(settings, key)
setattr(settings, key, value)
wrapper = backend.DatabaseWrapper()
wrapper._cursor(settings)
_connections[self.database] = wrapper
for key, value in backup.iteritems():
setattr(settings, key, value)
return _connections[self.database]
def _insert(self, values, return_id=False, raw_values=False):
query = sql.InsertQuery(self.model, self.get_db_wrapper())
query.insert_values(values, raw_values)
ret = query.execute_sql(return_id)
query.connection._commit()
thread_ident = thread.get_ident()
if thread_ident in savepoint_state:
del savepoint_state[thread_ident]
return ret
Then all you need to do is put the database connection details in
settings.py:
DATABASE_ENGINE = 'mysql'
DATABASE_NAME = 'db1'
DATABASE_USER = 'auser'
DATABASE_PASSWORD = 'somepassword'
DATABASE_HOST = ''
DATABASE_PORT = ''
DATABASES = dict(
db1 = dict(
DATABASE_ENGINE=DATABASE_ENGINE,
DATABASE_NAME=DATABASE_NAME,
DATABASE_USER=DATABASE_USER,
DATABASE_PASSWORD=DATABASE_PASSWORD,
DATABASE_HOST=DATABASE_HOST,
DATABASE_PORT=DATABASE_PORT,
),
db2 = dict(
DATABASE_ENGINE="mysql",
DATABASE_NAME='db2',
DATABASE_USER='anotheruser',
DATABASE_PASSWORD='password',
DATABASE_HOST='',
DATABASE_PORT='',
),
)
It seems to have worked for me so far. Obviously this is not a long
term solution, just something to get by with until Alex's code is
ready =)
Em
[1] http://code.djangoproject.com/ticket/1142#comment:65
[2] http://www.eflorenzano.com/blog/post/easy-multi-database-support-django/
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