Make sure we are using the adapter's column hash in AR 3.0

lib/ransack/adapters/active_record/3.0/context.rb

@@ -53,16 +53,8 @@ module Ransack
         end
 
         def type_for(attr)
-          return nil unless attr
-          name    = attr.name.to_s
-          table   = attr.relation.name
-
-          unless @engine.connection.table_exists?(table)
-            raise "No table named #{table} exists"
-          end
-
-          # TODO: optimize
-          @engine.connection.columns(table).detect {|c| c.name == name}.type
+          return nil unless attr && attr.valid?
+          klassify(attr.parent).columns_hash[attr.arel_attribute.name.to_s].type
         end
 
         private

lib/ransack/adapters/active_record/context.rb

@@ -51,9 +51,9 @@ module Ransack
         end
 
         def type_for(attr)
-          return nil unless attr
-          name    = attr.name.to_s
-          table   = attr.relation.table_name
+          return nil unless attr && attr.valid?
+          name    = attr.arel_attribute.name.to_s
+          table   = attr.arel_attribute.relation.table_name
 
           unless @engine.connection_pool.table_exists?(table)
             raise "No table named #{table} exists"

lib/ransack/nodes/attribute.rb

@@ -26,7 +26,7 @@ module Ransack
         if ransacker
           return ransacker.type
         else
-          context.type_for(attr)
+          context.type_for(self)
         end
       end
 

lib/ransack/nodes/bindable.rb

@@ -7,6 +7,7 @@ module Ransack
       def attr
         @attr ||= ransacker ? ransacker.attr_from(self) : context.table_for(parent)[attr_name]
       end
+      alias :arel_attribute :attr
 
       def ransacker
         klass._ransackers[attr_name]

lib/ransack/version.rb

@@ -1,3 +1,3 @@
 module Ransack
-  VERSION = "0.2.0"
+  VERSION = "0.2.1"
 end