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【Rails】COLLATE=utf8mb4_binなテーブルを作成するマイグレーションファイルの書き方

Posted at

MySQLには寿司ビール問題があります。
データベースの DEFAULT COLLATE を変更できれば一番いいんですが、それができない場合も多いと思います。
暫定対策として、COLLATE=utf8mb4_binなテーブルを作成するマイグレーションファイルの書き方です。

環境

  • Rails 6.1.3.2
  • MySQL 5.7.16

マイグレーションファイル

create_table に options: 'COLLATE utf8mb4_bin' を渡せばOKです。

class CreateTags < ActiveRecord::Migration[6.1]
  def change
    create_table :tags, options: 'COLLATE utf8mb4_bin' do |t|
      t.string :name, null: false, index: { unique: true }
      t.timestamps
    end
  end
end

db/schema.rb を確認

ちゃんと collation: "utf8mb4_bin" が入ってますね。

db/schema.rb
  create_table "tags", charset: "utf8mb4", collation: "utf8mb4_bin", force: :cascade do |t|
    t.string "name", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["name"], name: "index_tags_on_name", unique: true
  end

テーブル構造を確認

本当に COLLATE=utf8mb4_binが設定されているか、mysql上でも確認してみましょう。

mysql> SHOW FULL COLUMNS FROM tags;
+------------+--------------+-------------+------+-----+---------+----------------+---------------------------------+---------+
| Field      | Type         | Collation   | Null | Key | Default | Extra          | Privileges                      | Comment |
+------------+--------------+-------------+------+-----+---------+----------------+---------------------------------+---------+
| id         | bigint(20)   | NULL        | NO   | PRI | NULL    | auto_increment | select,insert,update,references |         |
| name       | varchar(255) | utf8mb4_bin | NO   | UNI | NULL    |                | select,insert,update,references |         |
| created_at | datetime(6)  | NULL        | NO   |     | NULL    |                | select,insert,update,references |         |
| updated_at | datetime(6)  | NULL        | NO   |     | NULL    |                | select,insert,update,references |         |
+------------+--------------+-------------+------+-----+---------+----------------+---------------------------------+---------+
4 rows in set (0.01 sec)

name カラムの Collation が utf8mb4_bin になってますね。

🍣 ≠ 🍺 になっているか確認

🍣 と 🍺 をINSERTしてみましょう。

mysql> INSERT INTO tags (name, created_at, updated_at) VALUES ('🍣', NOW(), NOW());
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO tags (name, created_at, updated_at) VALUES ('🍺', NOW(), NOW());
Query OK, 1 row affected (0.00 sec)

mysql> SELECT * FROM tags;
+----+------+----------------------------+----------------------------+
| id | name | created_at                 | updated_at                 |
+----+------+----------------------------+----------------------------+
|  1 | 🍣     | 2021-07-02 11:45:15.000000 | 2021-07-02 11:45:15.000000 |
|  2 | 🍺     | 2021-07-02 11:45:30.000000 | 2021-07-02 11:45:30.000000 |
+----+------+----------------------------+----------------------------+
2 rows in set (0.00 sec)

無事両方入りました! :sushi: :beer:

参考

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