speeding up query cache

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

@@ -59,14 +59,13 @@ def select_all(sql, name = nil, binds = [])
 
       private
         def cache_sql(sql, binds)
-          key = [sql, binds]
           result =
-            if @query_cache.has_key?(key)
+            if @query_cache[sql].key?(binds)
               ActiveSupport::Notifications.instrument("sql.active_record",
                 :sql => sql, :name => "CACHE", :connection_id => self.object_id)
-              @query_cache[key]
+              @query_cache[sql][binds]
             else
-              @query_cache[key] = yield
+              @query_cache[sql][binds] = yield
             end
 
           if Array === result

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -41,7 +41,7 @@ def initialize(connection, logger = nil) #:nodoc:
         @active = nil
         @connection, @logger = connection, logger
         @query_cache_enabled = false
-        @query_cache = {}
+        @query_cache = Hash.new { |h,sql| h[sql] = {} }
         @instrumenter = ActiveSupport::Notifications.instrumenter
       end