remove performance overrides of select_one, select_value, and select_values in the AR adapter for now

lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -264,28 +264,33 @@ module ActiveRecord
 
       # DATABASE STATEMENTS ======================================
 
-      # Returns a record hash with the column names as keys and column values
-      # as values.
-      def select_one(sql, name = nil)
-        result = execute(sql, name)
-        result.each(:as => :hash) do |r|
-          return r
-        end
-      end
-
-      # Returns a single value from a record
-      def select_value(sql, name = nil)
-        result = execute(sql, name)
-        if first = result.first
-          first.first
-        end
-      end
-
-      # Returns an array of the values of the first column in a select:
-      #   select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
-      def select_values(sql, name = nil)
-        execute(sql, name).map { |row| row.first }
-      end
+      # FIXME: re-enable the following once a "better" query_cache solution is in core
+      #
+      # The overrides below perform much better than the originals in AbstractAdapter
+      # because we're able to take advantage of mysql2's lazy-loading capabilities
+      #
+      # # Returns a record hash with the column names as keys and column values
+      # # as values.
+      # def select_one(sql, name = nil)
+      #   result = execute(sql, name)
+      #   result.each(:as => :hash) do |r|
+      #     return r
+      #   end
+      # end
+      # 
+      # # Returns a single value from a record
+      # def select_value(sql, name = nil)
+      #   result = execute(sql, name)
+      #   if first = result.first
+      #     first.first
+      #   end
+      # end
+      # 
+      # # Returns an array of the values of the first column in a select:
+      # #   select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
+      # def select_values(sql, name = nil)
+      #   execute(sql, name).map { |row| row.first }
+      # end
 
       # Returns an array of arrays containing the field values.
       # Order is the same as that returned by +columns+.