concurrent_index

🚀 Add Index Concurrently

Rails wraps migrations in transactions by default on PostgreSQL, but creating indexes concurrently requires disabling the transaction wrap. You can call disable_ddl_transaction! and specify algorithm: :concurrently to reduce downtime. This approach ensures the index build does not block writes on large tables.

class AddIndexToUsersEmailConcurrently < ActiveRecord::Migration[6.1]
  disable_ddl_transaction!

  def up
    add_index :users, :email, unique: true, algorithm: :concurrently
  end

  def down
    remove_index :users, :email, algorithm: :concurrently
  end
end