Optimisation for BigDecimal conversion code. Closes #11110 [adymo]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8870 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -4,6 +4,8 @@
 
 * Improve associations performance by avoiding named block arguments.  #11109 [adymo]
 
+* Optimise the BigDecimal conversion code.  #11110 [adymo]
+
 * Introduce the :readonly option to all associations. Records from the association cannot be saved.  #11084 [miloops]
 
 * Multiparameter attributes for time columns fail over to DateTime when out of range of Time [Geoff Buesing]

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -144,7 +144,10 @@ def value_to_boolean(value)
 
         # convert something to a BigDecimal
         def value_to_decimal(value)
-          if value.is_a?(BigDecimal)
+          # Using .class is faster than .is_a? and
+          # subclasses of BigDecimal will be handled
+          # in the else clause
+          if value.class == BigDecimal
             value
           elsif value.respond_to?(:to_d)
             value.to_d