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Rails 6.0 was recently released.
Before moving forward, we need to understand what the touch method does. touch is used to
update the updated_at
timestamp by defaulting to the current time. It also takes custom time or different columns as parameters.
Rails 6 has added touch_all on ActiveRecord::Relation to touch multiple records in one go. Before Rails 6, we needed to iterate all records using an iterator to achieve this result.
Let's take an example in which we call touch_all on all user records.
1>> User.count
2SELECT COUNT(\*) FROM "users"
3
4=> 3
5
6>> User.all.touch_all
7
8=> Traceback (most recent call last):1: from (irb):2
9NoMethodError (undefined method 'touch_all' for #<User::ActiveRecord_Relation:0x00007fe6261f9c58>)
10
11>> User.all.each(&:touch)
12SELECT "users".* FROM "users"
13begin transaction
14 UPDATE "users" SET "updated_at" = ? WHERE "users"."id" = ? [["updated_at", "2019-03-05 17:45:51.495203"], ["id", 1]]
15commit transaction
16begin transaction
17 UPDATE "users" SET "updated_at" = ? WHERE "users"."id" = ? [["updated_at", "2019-03-05 17:45:51.503415"], ["id", 2]]
18commit transaction
19begin transaction
20 UPDATE "users" SET "updated_at" = ? WHERE "users"."id" = ? [["updated_at", "2019-03-05 17:45:51.509058"], ["id", 3]]
21commit transaction
22
23=> [#<User id: 1, name: "Sam", created_at: "2019-03-05 16:09:29", updated_at: "2019-03-05 17:45:51">, #<User id: 2, name: "John", created_at: "2019-03-05 16:09:43", updated_at: "2019-03-05 17:45:51">, #<User id: 3, name: "Mark", created_at: "2019-03-05 16:09:45", updated_at: "2019-03-05 17:45:51">]
1>> User.count
2SELECT COUNT(*) FROM "users"
3
4=> 3
5
6>> User.all.touch_all
7UPDATE "users" SET "updated_at" = ? [["updated_at", "2019-03-05 16:08:47.490507"]]
8
9=> 3
touch_all returns count of the records on which it is called.
touch_all also takes a custom time or different columns as parameters.
1>> User.count
2SELECT COUNT(*) FROM "users"
3
4=> 3
5
6>> User.all.touch_all(time: Time.new(2019, 3, 2, 1, 0, 0))
7UPDATE "users" SET "updated_at" = ? [["updated_at", "2019-03-02 00:00:00"]]
8
9=> 3
10
11>> User.all.touch_all(:created_at)
12UPDATE "users" SET "updated_at" = ?, "created_at" = ? [["updated_at", "2019-03-05 17:55:41.828347"], ["created_at", "2019-03-05 17:55:41.828347"]]
13
14=> 3
Here is the relevant pull request.