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```
# 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.
|
