[Rails] Implementation of validation that maintains uniqueness

Tasks required to implement unique validation

  1. Described on the application side (uniqueness: true)
  2. Described on the database side (unique: true)

Described on the application side

models/user.rb


validates :email, uniqueness: true

Described on the database side

$ rails g migration add_column_to_users

add_column_to_users.rb


def change
  add_index :users, :email, unique: true
end

$ rails db:migrate

** Indexing ** is also required to make the columns of the table unique. The reason is that by searching all the data, you can check if it is duplicated with the past data.

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