[multi-db] Added optional db_connection property to model Meta classes,

which can be used to set the name of the connection for the  model. 
Updated query generation in model, query and fields/related to 
use the model's connection and backend. Added basic model connection 
access to multiple db test.


git-svn-id: http://code.djangoproject.com/svn/django/branches/multiple-db-support@3234 bcc190cf-cafb-0310-a4f2-bffc1f526a37

5 files changed, 138 insertions, 22 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 09e8eb3fc0..883ed7c81a 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -7,7 +7,7 @@ from django.db.models.fields.related import OneToOneRel, ManyToOneRel
 from django.db.models.related import RelatedObject
 from django.db.models.query import orderlist2sql, delete_objects
 from django.db.models.options import Options, AdminOptions
-from django.db import connection, backend, transaction
+from django.db import transaction
 from django.db.models import signals
 from django.db.models.loading import register_models, get_model
 from django.dispatch import dispatcher
@@ -158,6 +158,9 @@ class Model(object):
     def save(self):
         dispatcher.send(signal=signals.pre_save, sender=self.__class__, instance=self)
 
+        info = self._meta.connection_info
+        connection = info.connection
+        backend = info.backend
         non_pks = [f for f in self._meta.fields if not f.primary_key]
         cursor = connection.cursor()
 
@@ -205,7 +208,7 @@ class Model(object):
                      backend.get_pk_default_value()))
             if self._meta.has_auto_field and not pk_set:
                 setattr(self, self._meta.pk.attname, backend.get_last_insert_id(cursor, self._meta.db_table, self._meta.pk.column))
-        transaction.commit_unless_managed()
+        transaction.commit_unless_managed([connection])
 
         # Run any post-save hooks.
         dispatcher.send(signal=signals.post_save, sender=self.__class__, instance=self)
@@ -276,6 +279,7 @@ class Model(object):
         return dict(field.choices).get(value, value)
 
     def _get_next_or_previous_by_FIELD(self, field, is_next, **kwargs):
+        backend = self._meta.connection_info.backend
         op = is_next and '>' or '<'
         where = '(%s %s %%s OR (%s = %%s AND %s.%s %s %%s))' % \
             (backend.quote_name(field.column), op, backend.quote_name(field.column),
@@ -290,6 +294,7 @@ class Model(object):
             raise self.DoesNotExist, "%s matching query does not exist." % self.__class__._meta.object_name
 
     def _get_next_or_previous_in_order(self, is_next):
+        backend = self._meta.connection_info.backend
         cachename = "__%s_order_cache" % is_next
         if not hasattr(self, cachename):
             op = is_next and '>' or '<'
@@ -378,6 +383,9 @@ class Model(object):
         rel = rel_field.rel.to
         m2m_table = rel_field.m2m_db_table()
         this_id = self._get_pk_val()
+        info = self._meta.connection_info
+        connection = info.connection
+        backend = info.backend
         cursor = connection.cursor()
         cursor.execute("DELETE FROM %s WHERE %s = %%s" % \
             (backend.quote_name(m2m_table),
@@ -387,7 +395,7 @@ class Model(object):
             backend.quote_name(rel_field.m2m_column_name()),
             backend.quote_name(rel_field.m2m_reverse_name()))
         cursor.executemany(sql, [(this_id, i) for i in id_list])
-        transaction.commit_unless_managed()
+        transaction.commit_unless_managed([connection])
 
 ############################################
 # HELPER FUNCTIONS (CURRIED MODEL METHODS) #
@@ -396,6 +404,9 @@ class Model(object):
 # ORDERING METHODS #########################
 
 def method_set_order(ordered_obj, self, id_list):
+    connection_info = ordered_obj._meta.connection_info
+    connection = info.connection
+    backend = info.backend    
     cursor = connection.cursor()
     # Example: "UPDATE poll_choices SET _order = %s WHERE poll_id = %s AND id = %s"
     sql = "UPDATE %s SET %s = %%s WHERE %s = %%s AND %s = %%s" % \
@@ -404,9 +415,12 @@ def method_set_order(ordered_obj, self, id_list):
         backend.quote_name(ordered_obj._meta.pk.column))
     rel_val = getattr(self, ordered_obj._meta.order_with_respect_to.rel.field_name)
     cursor.executemany(sql, [(i, rel_val, j) for i, j in enumerate(id_list)])
-    transaction.commit_unless_managed()
+    transaction.commit_unless_managed([connection])
 
 def method_get_order(ordered_obj, self):
+    connection_info = ordered_obj.connection_info
+    connection = info.connection
+    backend = info.backend
     cursor = connection.cursor()
     # Example: "SELECT id FROM poll_choices WHERE poll_id = %s ORDER BY _order"
     sql = "SELECT %s FROM %s WHERE %s = %%s ORDER BY %s" % \
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 5ee1aec022..f7ca012351 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -1,4 +1,4 @@
-from django.db import backend, connection, transaction
+from django.db import transaction
 from django.db.models import signals, get_model
 from django.db.models.fields import AutoField, Field, IntegerField, get_ul_class
 from django.db.models.related import RelatedObject
@@ -290,7 +290,7 @@ def create_many_related_manager(superclass):
             # source_col_name: the PK colname in join_table for the source object
             # target_col_name: the PK colname in join_table for the target object
             # *objs - objects to add
-            from django.db import connection
+            connection = self.model._meta.connection
 
             # Add the newly created or already existing objects to the join table.
             # First find out which items are already added, to avoid adding them twice
@@ -310,13 +310,13 @@ def create_many_related_manager(superclass):
                 cursor.execute("INSERT INTO %s (%s, %s) VALUES (%%s, %%s)" % \
                     (self.join_table, source_col_name, target_col_name),
                     [self._pk_val, obj_id])
-            transaction.commit_unless_managed()
+            transaction.commit_unless_managed(connection)
 
         def _remove_items(self, source_col_name, target_col_name, *objs):
             # source_col_name: the PK colname in join_table for the source object
             # target_col_name: the PK colname in join_table for the target object
             # *objs - objects to remove
-            from django.db import connection
+            connection = self.model._meta.connection
 
             for obj in objs:
                 if not isinstance(obj, self.model):
@@ -327,16 +327,16 @@ def create_many_related_manager(superclass):
                 cursor.execute("DELETE FROM %s WHERE %s = %%s AND %s = %%s" % \
                     (self.join_table, source_col_name, target_col_name),
                     [self._pk_val, obj._get_pk_val()])
-            transaction.commit_unless_managed()
+            transaction.commit_unless_managed(connection)
 
         def _clear_items(self, source_col_name):
             # source_col_name: the PK colname in join_table for the source object
-            from django.db import connection
+            connection = self.model._meta.connection
             cursor = connection.cursor()
             cursor.execute("DELETE FROM %s WHERE %s = %%s" % \
                 (self.join_table, source_col_name),
                 [self._pk_val])
-            transaction.commit_unless_managed()
+            transaction.commit_unless_managed(connection)
 
     return ManyRelatedManager
 
@@ -360,6 +360,7 @@ class ManyRelatedObjectsDescriptor(object):
         superclass = rel_model._default_manager.__class__
         RelatedManager = create_many_related_manager(superclass)
 
+        backend = rel_model._meta.connection_info.backend
         qn = backend.quote_name
         manager = RelatedManager(
             model=rel_model,
@@ -402,6 +403,7 @@ class ReverseManyRelatedObjectsDescriptor(object):
         superclass = rel_model._default_manager.__class__
         RelatedManager = create_many_related_manager(superclass)
 
+        backend = rel_model._meta.connection_info.backend
         qn = backend.quote_name
         manager = RelatedManager(
             model=rel_model,
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 46a321f170..818bb62441 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -1,4 +1,5 @@
 from django.conf import settings
+from django.db import connection_info, connections
 from django.db.models.related import RelatedObject
 from django.db.models.fields.related import ManyToManyRel
 from django.db.models.fields import AutoField, FieldDoesNotExist
@@ -11,7 +12,7 @@ import re
 # Calculate the verbose_name by converting from InitialCaps to "lowercase with spaces".
 get_verbose_name = lambda class_name: re.sub('(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|$)))', ' \\1', class_name).lower().strip()
 
-DEFAULT_NAMES = ('verbose_name', 'db_table', 'ordering',
+DEFAULT_NAMES = ('verbose_name', 'db_connection', 'db_table', 'ordering',
                  'unique_together', 'permissions', 'get_latest_by',
                  'order_with_respect_to', 'app_label')
 
@@ -20,6 +21,7 @@ class Options(object):
         self.fields, self.many_to_many = [], []
         self.module_name, self.verbose_name = None, None
         self.verbose_name_plural = None
+        self.db_connection = None
         self.db_table = ''
         self.ordering = []
         self.unique_together =  []
@@ -90,6 +92,17 @@ class Options(object):
         
     def __str__(self):
         return "%s.%s" % (self.app_label, self.module_name)
+
+    def get_connection_info(self):
+        if self.db_connection:
+            return connections[self.db_connection]
+        return connection_info
+    connection_info = property(get_connection_info)
+            
+    def get_connection(self):
+        """Get the database connection for this object's model"""
+        return self.get_connection_info().connection
+    connection = property(get_connection)
         
     def get_field(self, name, many_to_many=True):
         "Returns the requested field by name. Raises FieldDoesNotExist on error."
diff --git a/django/db/models/query.py b/django/db/models/query.py
index efbe68cb66..8efdcd11e1 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -1,4 +1,4 @@
-from django.db import backend, connection, transaction
+from django.db import transaction
 from django.db.models.fields import DateField, FieldDoesNotExist
 from django.db.models import signals
 from django.dispatch import dispatcher
@@ -157,8 +157,7 @@ class QuerySet(object):
         # self._select is a dictionary, and dictionaries' key order is
         # undefined, so we convert it to a list of tuples.
         extra_select = self._select.items()
-
-        cursor = connection.cursor()
+        cursor = self.model._meta.connection.cursor()
         select, sql, params = self._get_sql_clause()
         cursor.execute("SELECT " + (self._distinct and "DISTINCT " or "") + ",".join(select) + sql, params)
         fill_cache = self._select_related
@@ -178,6 +177,9 @@ class QuerySet(object):
 
     def count(self):
         "Performs a SELECT COUNT() and returns the number of records as an integer."
+        info = self.model._meta.connection_info
+        backend = info.backend
+        connection = info.connection        
         counter = self._clone()
         counter._order_by = ()
         counter._offset = None
@@ -247,6 +249,7 @@ class QuerySet(object):
         Returns a dictionary mapping each of the given IDs to the object with
         that ID.
         """
+        backend = self.model._meta.connection_info.backend
         assert self._limit is None and self._offset is None, \
                 "Cannot use 'limit' or 'offset' with in_bulk"
         assert isinstance(id_list, (tuple,  list)), "in_bulk() must be provided with a list of IDs."
@@ -423,7 +426,7 @@ class QuerySet(object):
 
     def _get_sql_clause(self):
         opts = self.model._meta
-
+        backend = opts.connection_info.backend
         # Construct the fundamental parts of the query: SELECT X FROM Y WHERE Z.
         select = ["%s.%s" % (backend.quote_name(opts.db_table), backend.quote_name(f.column)) for f in opts.fields]
         tables = [quote_only_if_word(t) for t in self._tables]
@@ -514,6 +517,9 @@ class ValuesQuerySet(QuerySet):
             columns = [f.column for f in self.model._meta.fields]
             field_names = [f.attname for f in self.model._meta.fields]
 
+        info = self.model._meta.connection_info
+        backend = info.backend
+        connection = info.connection
         cursor = connection.cursor()
         select, sql, params = self._get_sql_clause()
         select = ['%s.%s' % (backend.quote_name(self.model._meta.db_table), backend.quote_name(c)) for c in columns]
@@ -533,6 +539,10 @@ class ValuesQuerySet(QuerySet):
 class DateQuerySet(QuerySet):
     def iterator(self):
         from django.db.backends.util import typecast_timestamp
+        info = self.model._meta.connection_info
+        backend = info.backend
+        connection = info.connection
+        
         self._order_by = () # Clear this because it'll mess things up otherwise.
         if self._field.null:
             self._where.append('%s.%s IS NOT NULL' % \
@@ -625,7 +635,9 @@ class QNot(Q):
         where2 = ['(NOT (%s))' % " AND ".join(where)]
         return tables, joins, where2, params
 
-def get_where_clause(lookup_type, table_prefix, field_name, value):
+def get_where_clause(opts, lookup_type, table_prefix, field_name, value):
+    backend = opts.connection_info.backend
+    
     if table_prefix.endswith('.'):
         table_prefix = backend.quote_name(table_prefix[:-1])+'.'
     field_name = backend.quote_name(field_name)
@@ -660,6 +672,7 @@ def fill_table_cache(opts, select, tables, where, old_prefix, cache_tables_seen)
     Helper function that recursively populates the select, tables and where (in
     place) for fill-cache queries.
     """
+    backend = opts.connection_info.backend
     for f in opts.fields:
         if f.rel and not f.null:
             db_table = f.rel.to._meta.db_table
@@ -753,6 +766,9 @@ def lookup_inner(path, clause, value, opts, table, column):
     current_column = column
     intermediate_table = None
     join_required = False
+    info = current_opts.connection_info
+    backend = info.backend
+    connection = info.connection
 
     name = path.pop(0)
     # Has the primary key been requested? If so, expand it out
@@ -881,7 +897,7 @@ def lookup_inner(path, clause, value, opts, table, column):
         else:
             column = field.column
 
-        where.append(get_where_clause(clause, current_table + '.', column, value))
+        where.append(get_where_clause(current_opts, clause, current_table + '.', column, value))
         params.extend(field.get_db_prep_lookup(clause, value))
 
     return tables, joins, where, params
@@ -891,9 +907,12 @@ def delete_objects(seen_objs):
     ordered_classes = seen_objs.keys()
     ordered_classes.reverse()
 
-    cursor = connection.cursor()
-
     for cls in ordered_classes:
+        info = cls._meta.connection_info
+        backend = info.backend
+        connection = info.connection
+        cursor = connection.cursor()
+        
         seen_objs[cls] = seen_objs[cls].items()
         seen_objs[cls].sort()
 
@@ -927,7 +946,16 @@ def delete_objects(seen_objs):
                         pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE])
 
     # Now delete the actual data
+    dirty_conns = []
     for cls in ordered_classes:
+
+        info = cls._meta.connection_info
+        backend = info.backend
+        connection = info.connection
+        cursor = connection.cursor()
+        if connection not in dirty_conns:
+            dirty_conns.append(connection)
+            
         seen_objs[cls].reverse()
         pk_list = [pk for pk,instance in seen_objs[cls]]
         for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
@@ -947,4 +975,4 @@ def delete_objects(seen_objs):
             setattr(instance, cls._meta.pk.attname, None)
             dispatcher.send(signal=signals.post_delete, sender=cls, instance=instance)
 
-    transaction.commit_unless_managed()
+    transaction.commit_unless_managed(dirty_conns)
diff --git a/tests/othertests/multiple_databases.py b/tests/othertests/multiple_databases.py
index 4e0919ae8f..be52757406 100644
--- a/tests/othertests/multiple_databases.py
+++ b/tests/othertests/multiple_databases.py
@@ -50,7 +50,7 @@ with the attributes: `DatabaseError`, `backend`,
 `runshell`. Access connections through the `connections` property of
 the `django.db` module:
 
-    >>> from django.db import connections
+    >>> from django.db import connection, connections
     >>> connections['a'].settings.DATABASE_NAME == db_a
     True
     >>> connections['b'].settings.DATABASE_NAME == db_b
@@ -62,6 +62,65 @@ Invalid connection names raise ImproperlyConfigured:
     Traceback (most recent call last):
         ...
     ImproperlyConfigured: No database connection 'bad' has been configured
+
+Models can define which connection to use, by name. To use a named
+connection, set the `db_connection` property in the model's Meta class
+to the name of the connection. The name used must be a key in
+settings.DATABASES, of course.
+
+    >>> from django.db import models
+    >>> class Artist(models.Model):
+    ...     name = models.CharField(maxlength=100)
+    ...     alive = models.BooleanField(default=True)
+    ...     
+    ...     def __str__(self):
+    ...         return self.name
+    ...    
+    ...     class Meta:
+    ...         app_label = 'mdb'
+    ...         db_connection = 'a'
+    ...
+    >>> class Widget(models.Model):
+    ...     code = models.CharField(maxlength=10, unique=True)
+    ...     weight = models.IntegerField()
+    ... 
+    ...     def __str__(self):
+    ...         return self.code
+    ... 
+    ...     class Meta:
+    ...         app_label = 'mdb'
+    ...         db_connection = 'b'
+    
+But they don't have to. Multiple database support is entirely optional
+and has no impact on your application if you don't use it.
+
+    >>> class Vehicle(models.Model):
+    ...     make = models.CharField(maxlength=20)
+    ...     model = models.CharField(maxlength=20)
+    ...     year = models.IntegerField()
+    ... 
+    ...     def __str__(self):
+    ...         return "%d %s %s" % (self.year, self.make, self.model)
+    ...     
+    ...     class Meta:
+    ...         app_label = 'mdb'
+
+    >>> Artist._meta.connection.settings.DATABASE_NAME == \
+    ...     connections['a'].connection.settings.DATABASE_NAME
+    True
+    >>> Widget._meta.connection.settings.DATABASE_NAME == \
+    ...     connections['b'].connection.settings.DATABASE_NAME
+    True
+    >>> Vehicle._meta.connection.settings.DATABASE_NAME == \
+    ...     connection.settings.DATABASE_NAME
+    True
+    >>> Artist._meta.connection.settings.DATABASE_NAME == \
+    ...     Widget._meta.connection.settings.DATABASE_NAME
+    False
+    >>> Artist._meta.connection.settings.DATABASE_NAME == \
+    ...     Vehicle._meta.connection.settings.DATABASE_NAME
+    False
+    
 """
 
 def cleanup():