1 files changed, 12 insertions, 3 deletions
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index ec5c189cd3..c5c4edd090 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -142,11 +142,20 @@ module ActiveRecord
         parents = model_cache[join_root]
         column_aliases = aliases.column_aliases join_root
 
-        result_set.each { |row_hash|
-          parent = parents[row_hash[primary_key]] ||= join_root.instantiate(row_hash, column_aliases)
-          construct(parent, join_root, row_hash, result_set, seen, model_cache, aliases)
+        message_bus = ActiveSupport::Notifications.instrumenter
+
+        payload = {
+          record_count: result_set.length,
+          class_name: join_root.base_klass.name
         }
 
+        message_bus.instrument('instantiation.active_record', payload) do
+          result_set.each { |row_hash|
+            parent = parents[row_hash[primary_key]] ||= join_root.instantiate(row_hash, column_aliases)
+            construct(parent, join_root, row_hash, result_set, seen, model_cache, aliases)
+          }
+        end
+
         parents.values
       end