User.find_each do |user|
  user.password = 'password'
  user.save
end

Devise.stretches = 1
User.find_each do |user|
  user.password = 'password'
  user.save
end
Devise.stretches = 10

sample_user = User.last
sample_user.password = "password"
encrypted_password = sample_user.encrypted_password
User.update_all(encrypted_password: encrypted_password)

ActiveRecord::Base.connection.execute(' update users set encrypted_password = 'password')

ActiveRecord::Base.connection.execute(' update users set password = md5('password'))