Update counter cache in memory if parent target is existed

Fixes #19550.

activerecord/lib/active_record/associations/builder/belongs_to.rb

@@ -31,24 +31,17 @@ def self.add_counter_cache_methods(mixin)
 
       mixin.class_eval do
         def belongs_to_counter_cache_after_update(reflection)
-          foreign_key  = reflection.foreign_key
-          cache_column = reflection.counter_cache_column
-
           if association(reflection.name).target_changed?
             if reflection.polymorphic?
-              model     = attribute_in_database(reflection.foreign_type).try(:constantize)
               model_was = attribute_before_last_save(reflection.foreign_type).try(:constantize)
             else
-              model     = reflection.klass
               model_was = reflection.klass
             end
 
-            foreign_key_was = attribute_before_last_save foreign_key
-            foreign_key     = attribute_in_database foreign_key
+            foreign_key_was = attribute_before_last_save(reflection.foreign_key)
+            cache_column = reflection.counter_cache_column
 
-            if foreign_key && model < ActiveRecord::Base
-              counter_cache_target(reflection, model, foreign_key).update_counters(cache_column => 1)
-            end
+            association(reflection.name).increment_counters
 
             if foreign_key_was && model_was < ActiveRecord::Base
               counter_cache_target(reflection, model_was, foreign_key_was).update_counters(cache_column => -1)

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -1197,6 +1197,38 @@ def test_counter_cache_updates_in_memory_after_create_with_array
     assert_equal 2, topic.reload.replies.size
   end
 
+  def test_counter_cache_updates_in_memory_after_update_with_inverse_of_disabled
+    topic = Topic.create!(title: "Zoom-zoom-zoom")
+
+    assert_equal 0, topic.replies_count
+
+    reply1 = Reply.create!(title: "re: zoom", content: "speedy quick!")
+    reply2 = Reply.create!(title: "re: zoom 2", content: "OMG lol!")
+
+    assert_queries(6) do
+      topic.replies << [reply1, reply2]
+    end
+
+    assert_equal 2, topic.replies_count
+    assert_equal 2, topic.reload.replies_count
+  end
+
+  def test_counter_cache_updates_in_memory_after_update_with_inverse_of_enabled
+    category = Category.create!(name: "Counter Cache")
+
+    assert_nil category.categorizations_count
+
+    categorization1 = Categorization.create!
+    categorization2 = Categorization.create!
+
+    assert_queries(4) do
+      category.categorizations << [categorization1, categorization2]
+    end
+
+    assert_equal 2, category.categorizations_count
+    assert_equal 2, category.reload.categorizations_count
+  end
+
   def test_pushing_association_updates_counter_cache
     topic = Topic.order("id ASC").first
     reply = Reply.create!