-
Notifications
You must be signed in to change notification settings - Fork 15
/
base.py
90 lines (76 loc) · 3.34 KB
/
base.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
from sqlalchemy import create_engine, MetaData, Table
# TODO support mutliple DBs via db.connections
class Bridge(object):
def __init__(self):
# prep the attributes, allowing them to be lazily loaded
self._meta = None
self._tables = {}
def connection_url(self):
"""Build a URL for :py:func:`sqlalchemy.create_engine`
based upon the database defined by :py:attr:`django.db.connection`
"""
# we lazily import connection since it requires a DJANGO_SETTINGS_MODULE
from django.db import connection
return urlbuild(
scheme=connection.vendor,
path=connection.settings_dict['NAME'],
username=connection.settings_dict['USER'],
password=connection.settings_dict['PASSWORD'],
hostname=connection.settings_dict['HOST'],
port=connection.settings_dict['PORT']
)
def _map_model(self, model_cls):
# TODO consider performance implications of autoloading schema
return Table(model_cls._meta.db_table, self.meta, autoload=True)
def __getitem__(self, model_cls):
"""Returns the :py:class:`sqlalchemy.schema.Table` representation
of ``model_cls``, a :py:class:`django.db.models.Model` subclass.
Use dict-notation to obtain the ``Table``::
>>> from myapp.models import mymodel
>>> brige = Bridge()
>>> mytable = bridge[mymodel]
>>> print type(mytable)
<class 'sqlalchemy.schema.Table'>
``Bridge`` stores the ``Table`` for the lifetime of the ``Bridge``,
thus table reflection only occurs once per model for the ``Bridge``.
"""
# not thread-safe, but at worst, we re-autoload the table
if model_cls not in self._tables:
self._tables[model_cls] = self._map_model(model_cls)
return self._tables[model_cls]
@property
def meta(self):
""":py:class:`sqlalchemy.schema.MetaData` instance bound to the current
Django database connection."""
# Lazily connect to the database. By waiting until meta is
# needed, we prevent capturing stale connection info from Django
# (e.g. during a TestCase)
if self._meta is None:
self._meta = MetaData()
self._meta.bind = create_engine(self.connection_url())
return self._meta
def urlbuild(scheme, path, username=None, password=None, hostname=None, port=None):
"""Builds a URL to pass into :py:func:`sqlalchemy.create_engine`
dialect+driver://username:password@host:port/database
"""
# we could use urlparse.ParseResult, but we would still need to manually
# build the whole netloc, so we don't gain much
# build the netloc depending on what parts we are given,
# later join the netloc together
netloc = []
if username:
netloc.append(username)
if password:
netloc.append(':')
netloc.append(password)
if username or password:
netloc.append('@')
if hostname:
netloc.append(hostname)
if port:
netloc.append(':')
netloc.append(str(port))
# put it all together
return '{scheme}://{netloc}/{path}'.format(scheme=scheme,
netloc=''.join(netloc),
path=path)