pluck
No Rails, temos o pluck, que retorna um array com os valores dos atributos que você selecionou.
Doctor.pluck(:id)
(0.9ms) SELECT "doctors"."id" FROM "doctors"
=> [1, 3, 7, 8, 9, 5]
Se você passa mais de um atributo, o pluck retorna um array com vários atributos.
Doctor.pluck(:id, :updated_at)
(0.5ms) SELECT "doctors"."id", "doctors"."updated_at" FROM "doctors"
=> [[1, Wed, 23 Jan 2019 11:44:27.924159000 EST -05:00],
[3, Tue, 29 Jan 2019 15:47:30.056920000 EST -05:00],
[7, Thu, 28 May 2020 19:30:29.238601000 EDT -04:00],
[8, Thu, 28 May 2020 19:30:29.251257000 EDT -04:00],
[9, Sat, 26 Jun 2021 19:56:41.536687000 EDT -04:00],
[5, Tue, 28 Jun 2022 16:49:45.091360000 EDT -04:00]]
A query é precisa, busca só os atributos que você pediu.
SELECT "doctors"."id", "doctors"."updated_at" FROM "doctors"
select
O select faz a mesma query.
Doctor.select(:id, :updated_at)
Doctor Load (0.3ms) SELECT "doctors"."id", "doctors"."updated_at" FROM "doctors"
Doctor.pluck(:id, :updated_at)
(0.3ms) SELECT "doctors"."id", "doctors"."updated_at" FROM "doctors"
Doctor.select(:id, :updated_at)
Doctor Load (0.6ms) SELECT "doctors"."id", "doctors"."updated_at" FROM "doctors"
=>[#<Doctor:0x0000000111a2ec40 id: 1, updated_at: Wed, 23 Jan 2019 11:44:27.924159000 EST -05:00>,
#<Doctor:0x0000000111a2eab0 id: 3, updated_at: Tue, 29 Jan 2019 15:47:30.056920000 EST -05:00>,
#<Doctor:0x0000000111a2e998 id: 7, updated_at: Thu, 28 May 2020 19:30:29.238601000 EDT -04:00>,
#<Doctor:0x0000000111a2e858 id: 8, updated_at: Thu, 28 May 2020 19:30:29.251257000 EDT -04:00>,
#<Doctor:0x0000000111a2e4c0 id: 9, updated_at: Sat, 26 Jun 2021 19:56:41.536687000 EDT -04:00>,
#<Doctor:0x0000000111a2e218 id: 5, updated_at: Tue, 28 Jun 2022 16:49:45.091360000 EDT -04:00>]
Mas o select retorna um ActiveRecord::Relation com objetos do model em que ele foi chamado.
Doctor.select(:id, :updated_at).class
=> Doctor::ActiveRecord_Relation
é isso, pessoal :)
Publicado originalmente em guilherme44.com.