Extract `default_extensions` to avoid `klass.all`

As @matthewd's suggestion, if `klass` has no default scope, it will more
faster.

2 files changed, 9 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index e42162c740..0f330af2f6 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -134,7 +134,7 @@ module ActiveRecord
       end
 
       def extensions
-        extensions = klass.all.extensions | reflection.extensions
+        extensions = klass.default_extensions | reflection.extensions
 
         if scope = reflection.scope
           extensions |= klass.unscoped.instance_exec(owner, &scope).extensions
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index d03c23fe5c..93c6f1d87e 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -34,6 +34,14 @@ module ActiveRecord
           build_default_scope(scope) || scope
         end
 
+        def default_extensions # :nodoc:
+          if scope = current_scope || build_default_scope
+            scope.extensions
+          else
+            []
+          end
+        end
+
         # Adds a class method for retrieving and querying objects.
         # The method is intended to return an ActiveRecord::Relation
         # object, which is composable with other scopes.