[Rails]multiple databases

2023-02-10

rails

Ruby on Raylsで複数DBを使いたいメモ

config/database.yml

コツ
* 接続情報をネストする
* migrations_paths でmigrationファイルの場所を分ける
* 接続だけしたい(migrationとか不要)ならdatabase_tasks: false


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development:
  main:
    <<: *default
    database: multi_db_db_main_development
    migrations_paths: db/main
    host: db_main
  sub:
    <<: *default
    database: multi_db_db_sub_development
    migrations_paths: db/sub
    host: db_sub
    # database_tasks: false

test:
  main:
    <<: *default
    database: multi_db_db_main_test
    migrations_paths: db/main
    host: db_main
  sub:
    <<: *default
    database: multi_db_db_sub_test
    migrations_paths: db/sub
    host: db_sub

production
 ...

generate

--databaseオプションを付与する
接続先を指定したApplicationRecordのサブクラスが一緒に作られる(なければ)
各モデルはApplicationRecordの孫クラスになる


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$ bin/rails g model dog name:string --database main
      invoke  active_record
      create    db/main/20230209193743_create_dogs.rb
      create    app/models/main_record.rb
      create    app/models/dog.rb

$ bin/rails g model cat name:string --database sub
      invoke  active_record
      create    db/sub/20230209194008_create_cats.rb
      create    app/models/sub_record.rb
      create    app/models/cat.rb

$ bin/rails g model tiger name:string --database sub
      invoke  active_record
      create    db/sub/20230209194036_create_tigers.rb
      create    app/models/tiger.rb

application_record.rb

例えばsubが管理外の既存データベースで、いきなりモデルを作成するような場合はMainRecordとSubRecordを手動で作成する必要がある。

main


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class MainRecord < ApplicationRecord
  self.abstract_class = true

  connects_to database: { writing: :main }
end

sub


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class SubRecord < ApplicationRecord
  self.abstract_class = true

  connects_to database: { writing: :sub }
  after_initialize :readonly! # dbへの書き込みを禁止したい場合
end

connects_to には readingオプションも渡せる。
リードレプリカに接続したいときに使う。

db create


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$ rails db:create
Created database 'multi_db_db_main_development'
Created database 'multi_db_db_sub_development'
Created database 'multi_db_db_main_test'
Created database 'multi_db_db_sub_test'

db migrate


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$ rails db:migrate
== 20230209193743 CreateDogs: migrating =======================================
-- create_table(:dogs)
   -> 0.0242s
== 20230209193743 CreateDogs: migrated (0.0243s) ==============================

== 20230209194008 CreateCats: migrating =======================================
-- create_table(:cats)
   -> 0.0232s
== 20230209194008 CreateCats: migrated (0.0233s) ==============================

== 20230209194036 CreateTigers: migrating =====================================
-- create_table(:tigers)
   -> 0.0250s
== 20230209194036 CreateTigers: migrated (0.0251s) ============================

データ登録してみる


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irb(main):001:0> Dog.create(name: '柴犬')
  TRANSACTION (0.2ms)  BEGIN
  Dog Create (0.4ms)  INSERT INTO `dogs` (`name`, `created_at`, `updated_at`) VALUES ('柴犬', '2023-02-09 19:42:27.364216', '2023-02-09 19:42:27.364216')
  TRANSACTION (5.0ms)  COMMIT
=> #<Dog:0x00007ffa2c8290f0 id: 1, name: "柴犬", created_at: Fri, 10 Feb 2023 04:42:27.364216000 JST +09:00, updated_at: Fri, 10 Feb 2023 04:42:27.364216000 JST +09:00>
irb(main):002:0> Cat.create(name: 'マンチカン')
  TRANSACTION (0.2ms)  BEGIN
  Cat Create (0.3ms)  INSERT INTO `cats` (`name`, `created_at`, `updated_at`) VALUES ('マンチカン', '2023-02-09 19:42:31.738822', '2023-02-09 19:42:31.738822')
  TRANSACTION (4.3ms)  COMMIT
=> #<Cat:0x00007ffa2c73e118 id: 1, name: "マンチカン", created_at: Fri, 10 Feb 2023 04:42:31.738822000 JST +09:00, updated_at: Fri, 10 Feb 2023 04:42:31.738822000 JST +09:00>

db接続して確認してみる