instance method `preload`

Ruby on Rails 7.1.6

Since v3.0.20

Available in: v3.0.20 v3.1.12 v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

preload(*args)

Specify associations args to be eager loaded using separate queries. A separate query is performed for each association.

users = User.preload(:address).limit(5)
users.each do |user|
  user.address.city
end

# SELECT "users".* FROM "users" LIMIT 5
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)

Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a separate query.

Loading multiple and nested associations is possible using Hashes and Arrays, similar to #includes:

User.preload(:address, friends: [:address, :followers])
# SELECT "users".* FROM "users"
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
# SELECT "friends".* FROM "friends" WHERE "friends"."user_id" IN (1,2,3,4,5)
# SELECT ...

Parameters

args rest

Source

# File activerecord/lib/active_record/relation/query_methods.rb, line 299
    def preload(*args)
      check_if_method_has_arguments!(__callee__, args)
      spawn.preload!(*args)
    end

Defined in activerecord/lib/active_record/relation/query_methods.rb line 299 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::QueryMethods

Signature

Parameters