Do not create useless database transaction when building `has_one` association.

1 files changed, 9 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index 06bead41de..ee816d2392 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -28,7 +28,7 @@ module ActiveRecord
         # If target and record are nil, or target is equal to record,
         # we don't need to have transaction.
         if (target || record) && target != record
-          reflection.klass.transaction do
+          transaction_if(save) do
             remove_target!(options[:dependent]) if target && !target.destroyed?
 
             if record
@@ -90,6 +90,14 @@ module ActiveRecord
         def nullify_owner_attributes(record)
           record[reflection.foreign_key] = nil
         end
+
+        def transaction_if(value)
+          if value
+            reflection.klass.transaction { yield }
+          else
+            yield
+          end
+        end
     end
   end
 end