gistfile1.py

import string
from random import SystemRandom
from django.db import connections

key_chars = string.ascii_letters
random = SystemRandom()

class adhoc_db(object):
    """Context manager that temporarily adds a database connection.

    Exceptions are passed through, but ensures the connection and
    settings have been cleaned up from `connections.databases`.
    
    Usage:
    
        with adhoc_db(settings) as conn:
            # do something with...

    """
    def __init__(self, settings, alias=None):
        if alias is None:
            key = ''.join(random.choice(key_chars) for i in xrange(10))

        # TODO should this lock?
        assert alias not in connections.databases or \
            connections.databases[alias] == settings

        self.alias = alias
        connections.databases[alias] = settings
        self.connection = connections[alias]

    def __enter__(self):
        return self.connection

    def __exit__(self, *excinfo):
        self.connection.close()
        del connections.databases[self.alias]
        
def adhoc_db_decorator(settings, alias=None):
    def decorator(func):
        def inner(*args, **kwargs):
            with adhoc_db(settings, alias):
                return func(*args, **kwargs)
        return inner
    return decorator