WIP - delay_touching on relationship table may cause "update where NULL" query

lib/activerecord/delay_touching.rb

@@ -95,7 +95,7 @@ def self.touch_records(attr, klass, records)
           end
         end
 
-        klass.unscoped.where(klass.primary_key => records).update_all(changes)
+        klass.unscoped.where(klass.primary_key => records.select(&:persisted?)).update_all(changes)
       end
       state.updated attr, records
       records.each { |record| record.run_callbacks(:touch) }

spec/activerecord/delay_touching_spec.rb

@@ -195,6 +195,24 @@
 
     end
 
+    it 'does not attempt to update is NULL primary key' do
+      bad_update = /UPDATE "tags" SET "updated_at" = .* WHERE "tags"\."id" IS NULL/
+      expect(ActiveRecord::Base.connection).to receive(:update).and_wrap_original do |m, *args|
+        arel_stmt = args.first
+        expect(arel_stmt.to_sql).to_not match(bad_update)
+        m.call(*args)
+      end
+
+      ActiveRecord::Base.delay_touching do
+        ActiveRecord::Base.transaction do
+          # touch any record through a custom relationship table
+          # NOTE: does not happen with a has_and_belongs_to_many relationship
+          post = Post.create!
+          post.tags.create!
+          raise ActiveRecord::Rollback
+        end
+      end
+    end
   end
 
   def expect_updates(tables)

spec/support/models.rb

@@ -8,6 +8,9 @@ class Pet < ActiveRecord::Base
 
 class Post < ActiveRecord::Base
   has_many :comments, dependent: :destroy
+
+  has_many :tag_relationships, dependent: :destroy
+  has_many :tags, through: :tag_relationships
 end
 
 class User < ActiveRecord::Base
@@ -18,3 +21,13 @@ class Comment < ActiveRecord::Base
   belongs_to :post, touch: true
   belongs_to :user, touch: true
 end
+
+class Tag < ActiveRecord::Base
+  has_many :tag_relationships, dependent: :destroy
+  has_many :posts, through: :tag_relationships
+end
+
+class TagRelationship < ActiveRecord::Base
+  belongs_to :tag, touch: true
+  belongs_to :post
+end

spec/support/schema.rb

@@ -30,4 +30,12 @@
     t.timestamps null: false
   end
 
+  create_table :tags, force: true do |t|
+    t.timestamps null: false
+  end
+
+  create_table :tag_relationships, force: true do |t|
+    t.integer :tag_id
+    t.integer :post_id
+  end
 end