Avoid iterating over records hash when not necessary

If the reflection scope is not flagged with distinct value, there is no
need to iterate over the records, so we avoid that by doing the check
before iterating rather than inside the iteration block.

1 files changed, 6 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/associations/preloader/has_many_through.rb b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
index 0dc551f100..157b627ad5 100644
--- a/activerecord/lib/active_record/associations/preloader/has_many_through.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
@@ -5,9 +5,13 @@ module ActiveRecord
         include ThroughAssociation
 
         def associated_records_by_owner
-          super.each_value do |records|
-            records.uniq! if reflection_scope.distinct_value
+          records_by_owner = super
+
+          if reflection_scope.distinct_value
+            records_by_owner.each_value { |records| records.uniq! }
           end
+
+          records_by_owner
         end
       end
     end