Fix conflicts `counter_cache` with `touch: true` by optimistic locking.

  ```
  # create_table :posts do |t|
  #   t.integer :comments_count, default: 0
  #   t.integer :lock_version
  #   t.timestamps
  # end
  class Post < ApplicationRecord
  end

  # create_table :comments do |t|
  #   t.belongs_to :post
  # end
  class Comment < ApplicationRecord
    belongs_to :post, touch: true, counter_cache: true
  end
  ```

  Before:
  ```
  post = Post.create!
  # => begin transaction
       INSERT INTO "posts" ("created_at", "updated_at", "lock_version")
       VALUES ("2017-12-11 21:27:11.387397", "2017-12-11 21:27:11.387397", 0)
       commit transaction

  comment = Comment.create!(post: post)
  # => begin transaction
       INSERT INTO "comments" ("post_id") VALUES (1)

       UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) + 1,
       "lock_version" = COALESCE("lock_version", 0) + 1 WHERE "posts"."id" = 1

       UPDATE "posts" SET "updated_at" = '2017-12-11 21:27:11.398330',
       "lock_version" = 1 WHERE "posts"."id" = 1 AND "posts"."lock_version" = 0
       rollback transaction
  # => ActiveRecord::StaleObjectError: Attempted to touch a stale object: Post.

  Comment.take.destroy!
  # => begin transaction
       DELETE FROM "comments" WHERE "comments"."id" = 1

       UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) - 1,
       "lock_version" = COALESCE("lock_version", 0) + 1 WHERE "posts"."id" = 1

       UPDATE "posts" SET "updated_at" = '2017-12-11 21:42:47.785901',
       "lock_version" = 1 WHERE "posts"."id" = 1 AND "posts"."lock_version" = 0
       rollback transaction
  # => ActiveRecord::StaleObjectError: Attempted to touch a stale object: Post.
  ```

  After:
  ```
  post = Post.create!
  # => begin transaction
       INSERT INTO "posts" ("created_at", "updated_at", "lock_version")
       VALUES ("2017-12-11 21:27:11.387397", "2017-12-11 21:27:11.387397", 0)
       commit transaction

  comment = Comment.create!(post: post)
  # => begin transaction
       INSERT INTO "comments" ("post_id") VALUES (1)

       UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) + 1,
       "lock_version" = COALESCE("lock_version", 0) + 1,
       "updated_at" = '2017-12-11 21:37:09.802642' WHERE "posts"."id" = 1
       commit transaction

  comment.destroy!
  # => begin transaction
       DELETE FROM "comments" WHERE "comments"."id" = 1

       UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) - 1,
       "lock_version" = COALESCE("lock_version", 0) + 1,
       "updated_at" = '2017-12-11 21:39:02.685520' WHERE "posts"."id" = 1
       commit transaction
  ```

  Fixes #31199.

1 files changed, 2 insertions, 1 deletions

diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index bf66846840..3205c4c20a 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -123,7 +123,7 @@ ActiveRecord::Schema.define do
   create_table :cars, force: true do |t|
     t.string  :name
     t.integer :engines_count
-    t.integer :wheels_count
+    t.integer :wheels_count, default: 0
     t.column :lock_version, :integer, null: false, default: 0
     t.timestamps null: false
   end
@@ -964,6 +964,7 @@ ActiveRecord::Schema.define do
   end
 
   create_table :wheels, force: true do |t|
+    t.integer :size
     t.references :wheelable, polymorphic: true
   end