Should not update children when the parent creation with no reason

This issue was introduced with d849f42 to solve #19782. However, we can
solve #19782 without causing the issue. It is enough to save only when
necessary.

Fixes #27338.

1 files changed, 6 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 0c0aefe3b9..c4a7fe4432 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -38,10 +38,12 @@ module ActiveRecord
       def insert_record(record, validate = true, raise = false)
         ensure_not_nested
 
-        if raise
-          record.save!(validate: validate)
-        else
-          return unless record.save(validate: validate)
+        if record.new_record? || record.has_changes_to_save?
+          if raise
+            record.save!(validate: validate)
+          else
+            return unless record.save(validate: validate)
+          end
         end
 
         save_through_record(record)