fix associations when using per class databases

would get ConnectionNotEstablished error because it always tried to use
ActiveRecord::Base's connection, even though it should be using the connection
of the model whose context we're operating in

activerecord/lib/active_record/associations/alias_tracker.rb

@@ -5,12 +5,13 @@ module Associations
     # Keeps track of table aliases for ActiveRecord::Associations::ClassMethods::JoinDependency and
     # ActiveRecord::Associations::ThroughAssociationScope
     class AliasTracker # :nodoc:
-      attr_reader :aliases, :table_joins
+      attr_reader :aliases, :table_joins, :connection
 
       # table_joins is an array of arel joins which might conflict with the aliases we assign here
-      def initialize(table_joins = [])
+      def initialize(connection = ActiveRecord::Model.connection, table_joins = [])
         @aliases     = Hash.new { |h,k| h[k] = initial_count_for(k) }
         @table_joins = table_joins
+        @connection  = connection
       end
 
       def aliased_table_for(table_name, aliased_name = nil)
@@ -70,10 +71,6 @@ def initial_count_for(name)
         def truncate(name)
           name.slice(0, connection.table_alias_length - 2)
         end
-
-        def connection
-          ActiveRecord::Base.connection
-        end
     end
   end
 end

activerecord/lib/active_record/associations/association_scope.rb

@@ -10,7 +10,7 @@ class AssociationScope #:nodoc:
 
       def initialize(association)
         @association   = association
-        @alias_tracker = AliasTracker.new
+        @alias_tracker = AliasTracker.new klass.connection
       end
 
       def scope

activerecord/lib/active_record/associations/join_dependency.rb

@@ -13,7 +13,7 @@ def initialize(base, associations, joins)
         @join_parts    = [JoinBase.new(base)]
         @associations  = {}
         @reflections   = []
-        @alias_tracker = AliasTracker.new(joins)
+        @alias_tracker = AliasTracker.new(base.connection, joins)
         @alias_tracker.aliased_name_for(base.table_name) # Updates the count for base.table_name to 1
         build(associations)
       end