cache the instrumentor for a speed gain

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -44,6 +44,7 @@ module ActiveRecord
         @runtime = 0
         @query_cache_enabled = false
         @query_cache = {}
+        @instrumenter = ActiveSupport::Notifications.instrumenter
       end
 
       # Returns the human-readable name of the adapter.  Use mixed case - one
@@ -199,10 +200,9 @@ module ActiveRecord
 
         def log(sql, name)
           name ||= "SQL"
-          instrumenter = ActiveSupport::Notifications.instrumenter
           info = {}
 
-          result = instrumenter.instrument("sql.active_record",
+          result = @instrumenter.instrument("sql.active_record",
             {:sql => sql, :name => name, :connection_id => object_id}, info) do
             yield
           end