def new_backend(url, backend_args=None):
"""Return a new database backend instance for a file.
- `url`: URL of the database to open with the backend. If given
as just a filename, and the file already exists, then the
backend is auto-detected if possible, or an exception is raised.
If the file does not already exist and `None` is given, an
exception is raised.
- `backend_args`: (optional) Additional arguments to pass to the backend.
"""
if backend_args is None:
backend_args = {}
else:
backend_args = backend_args.copy()
if '://' not in url:
# Assume filename, try to find backend.
from schevo.backend import backends
usable = False
for backend_name, backend_class in backends.iteritems():
try:
usable = backend_class.usable_by_backend(url)
except IOError:
usable = False
else:
if usable:
usable, additional_args = usable
backend_args.update(additional_args)
# Convert to proper URL form.
url = '%s:///%s' % (backend_name, url)
break
if not usable:
raise IOError('No suitable backends found for %r' % url)
# Convert to URL object.
url = make_url(url)
# Convert backend args to a dictionary.
backend_args.update(url.translate_connect_args())
return url.backend_class()(**backend_args)
def backend_class(self):
return make_url(
self.backend_url).backend_class().TestMethods_EvolvesSchemata
def backend_class(self):
"""Return the appropriate backend class for this type of test."""
return make_url(
self.backend_url).backend_class().TestMethods_CreatesDatabase
