diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 52af1ea816..c9c7063a62 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,6 +1,8 @@
 *SVN*
 
-* Optimization for Mysql selects using mysql-ruby extension greater than 2.6.3.  #2426. [skaes.web.de]
+# Speed up for unthreaded environments. #2431. [skaes@web.de]
+
+* Optimization for Mysql selects using mysql-ruby extension greater than 2.6.3.  #2426. [skaes@web.de]
 
 * Speed up the setting of table_name. #2428. [skaes@web.de]
 
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index ab9b5d6221..b31844d1b7 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -235,7 +235,11 @@ module ActiveRecord #:nodoc:
     # also be used to "borrow" the connection to do database work unrelated
     # to any of the specific Active Records.
     def self.connection
-      retrieve_connection
+      if @@threaded_connections
+        retrieve_connection
+      else
+        @connection ||= retrieve_connection
+      end
     end
 
     # Returns the connection currently associated with the class. This can
@@ -928,15 +932,23 @@ module ActiveRecord #:nodoc:
         end
         
         def scope_constraints
-          Thread.current[:constraints] ||= {}
-          Thread.current[:constraints][self] ||= {}
+          if @@threaded_connections
+            Thread.current[:constraints] ||= {}
+            Thread.current[:constraints][self] ||= {}
+          else
+            @scope_constraints ||= {}
+          end
         end
         # backwards compatibility
         alias_method :scope_constrains, :scope_constraints 
 
         def scope_constraints=(value)
-          Thread.current[:constraints] ||= {}
-          Thread.current[:constraints][self] = value
+          if @@threaded_connections
+            Thread.current[:constraints] ||= {}
+            Thread.current[:constraints][self] = value
+          else
+            @scope_constraints = value
+          end
         end
         # backwards compatibility
         alias_method :scope_constrains=, :scope_constraints=