django.db.models.sql.where is using the global "connection" rather than the query object's "connection"

[crcradock]

I have need to use both MySQL database and an MS SQL server (via ODBC). I noticed some rather strange quirks which lead me to work out that django.db.models.sql.where is referring to the global "connection" rather than the query's connection. Primarily queries to the other database type appear to fail with incorrect "where" clauses.

Viz: assume MySQL is the default database as quoted in the project's settings.py file

import MSSQL.model
MSSQL.model.RandomTable.get(fieldstartswith='ticket')

Traceback (most recent call last):

File "<console>", line 1, in <module>
File "/usr/lib/python2.5/site-packages/django/db/models/manager.py", line 120, in get

return self.get_query_set().get(*args, kwargs)

File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 269, in get

num = len(clone)

File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 68, in len

self._result_cache = list(self.iterator())

File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 207, in iterator

for row in self.query.results_iter():

File "/usr/lib/python2.5/site-packages/django/db/models/sql/query.py", line 262, in results_iter

for rows in self.execute_sql(MULTI):

File "/usr/lib/python2.5/site-packages/django/db/models/sql/query.py", line 2294, in execute_sql

cursor.execute(sql, params)

File "/usr/lib/python2.5/site-packages/django/db/backends/util.py", line 19, in execute

return self.cursor.execute(sql, params)

File "/usr/lib/python2.5/site-packages/django/db/backends/py_odbc/base.py", line 226, in execute

return self.cursor.execute(sql, params)

ProgrammingError: ('42000', '[42000] [FreeTDS][SQL Server]Statement(s) could not be prepared. (8180) (SQLPrepare)')

Does anyone know how to find the correct connection in the "as_sql" subroutine in django.db.models.sql.where, or do we need to call django.db.models.sql.where.as_sql with the appropriate "connection" as a parameter?

Affected lines:
156: cast_sql = connection.ops.datetime_cast_sql()
166: if lookup_type in connection.operators:
167: format = "%s %%s %%s" % (connection.ops.lookup_cast(lookup_type),)
169: connection.operators[lookup_type] % cast_sql,
182: return ('%s = %%s' % connection.ops.date_extract_sql(lookup_type, field_sql),
188: return (connection.ops.fulltext_search_sql(field_sql), params)
190: return connection.ops.regex_lookup(lookup_type) % (field_sql, cast_sql), params
205: return connection.ops.field_cast_sql(db_type) % lhs

Just incase it has a bearing on the matter I'm using a DB-Manager for the tables of the form:

class ODBCManager(models.Manager):

use_for_related_fields = True
cached_connection = False
query = False

def get_query_set(self):

if( not self.cached_connection ):

h_connection=py_odbc.base.DatabaseWrapper( dict(

DATABASE_ODBC_DSN=settings.DATABASE_ODBC_DSN

,DATABASE_NAME=settings.DATABASE_ODBC_DATABASE
,DATABASE_OPTIONS=dict()

) )
h_query = h_connection.ops.query_class(sql.query.BaseQuery)
self.query = h_query(self.model, h_connection )
self.cached_connection = True

return QuerySet(self.model,self.query)