Fix non-partial inserts for models with composite identity primary keys

activerecord/lib/active_record/attribute_methods/dirty.rb

@@ -251,7 +251,7 @@ def attribute_names_for_partial_inserts
             changed_attribute_names_to_save
           else
             attribute_names.reject do |attr_name|
-              if column_for_attribute(attr_name).default_function
+              if column_for_attribute(attr_name).auto_populated?
                 !attribute_changed?(attr_name)
               end
             end

activerecord/test/cases/dirty_test.rb

@@ -972,6 +972,20 @@ def check_around
     end
   end
 
+  if current_adapter?(:PostgreSQLAdapter) && supports_identity_columns?
+    test "partial insert off with changed composite identity primary key attribute" do
+      klass = Class.new(ActiveRecord::Base) do
+        self.table_name = "cpk_postgresql_identity_table"
+      end
+
+      with_partial_writes(klass, false) do
+        record = klass.create!(another_id: 10)
+        assert_equal 10, record.another_id
+        assert_not_nil record.id
+      end
+    end
+  end
+
   test "attribute_changed? properly type casts enum values" do
     parrot = LiveParrot.create!(name: "Scipio", breed: :african)
 

activerecord/test/schema/postgresql_specific_schema.rb

@@ -53,6 +53,15 @@
         id INT PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY
       )
     SQL
+
+    drop_table "cpk_postgresql_identity_table", if_exists: true
+    execute <<~SQL
+      create table cpk_postgresql_identity_table (
+        another_id INT NOT NULL,
+        id INT NOT NULL GENERATED BY DEFAULT AS IDENTITY,
+        CONSTRAINT cpk_postgresql_identity_table_pkey PRIMARY KEY (another_id, id)
+      )
+    SQL
   end
 
   create_table :postgresql_times, force: true do |t|