mongo.rb in mongoid-3.0.3

- old
+ new

@@ -28,11 +28,11 @@
       #
       # @return [ true, false ] If the context is empty.
       #
       # @since 3.0.0
       def blank?
-        count == 0
+        !exists?
       end
       alias :empty? :blank?
 
       # Is the context cached?
       #
@@ -149,11 +149,12 @@
       #
       # @return [ true, false ] If the count is more than zero.
       #
       # @since 3.0.0
       def exists?
-        count > 0
+        # Don't use count here since Mongo does not use counted b-tree indexes
+        !query.dup.select(_id: 1).limit(1).entries.first.nil?
       end
 
       # Run an explain on the criteria.
       #
       # @example Explain the criteria.
@@ -212,11 +213,11 @@
       #
       # @since 3.0.0
       def initialize(criteria)
         @criteria, @klass, @cache = criteria, criteria.klass, criteria.options[:cache]
         @collection = klass.collection
-        add_type_selection
+        criteria.send(:merge_type_selection)
         @query = collection.find(criteria.selector)
         apply_options
       end
 
       # Get the last document in the database for the criteria's selector.
@@ -322,24 +323,9 @@
         query.update_all(attributes.__consolidate__)
       end
       alias :update_all :update
 
       private
-
-      # For models where inheritance is at play we need to add the type
-      # selection.
-      #
-      # @example Add the type selection.
-      #   context.add_type_selection
-      #
-      # @return [ true, false ] If type selection was added.
-      #
-      # @since 3.0.0
-      def add_type_selection
-        if klass.hereditary? && !criteria.selector.keys.include?(:_type)
-          criteria.selector.merge!(_type: { "$in" => klass._types })
-        end
-      end
 
       # Apply the field limitations.
       #
       # @api private
       #