first-migration.rb

class DropSubscriptionRewards < ActiveRecord::Migration[5.2]
  def up
    subscription_rewards = SubscriptionReward.all
    subscription_rewards.each do |subscription_reward|
      MissionReward.create!(
        subscription_mission_id: subscription_reward["subscription_mission_id"],
        reward_id: subscription_reward["reward_id"],
        starts_at: subscription_reward["created_at"],
        ends_at: subscription_reward["expires_at"],
        redeemed_at: subscription_reward["redeemed_at"]
      )
    end

    drop_table :subscription_rewards
  end

  def down
    raise ActiveRecord::IrreversibleMigration
  end
end