forgeplus/db/migrate/20200515082628_create_fork_users.rb

class CreateForkUsers < ActiveRecord::Migration[5.2]
  def change
    create_table :fork_users do |t|
      t.integer :project_id  #原始项目id
      t.integer :fork_project_id  #fork后的项目id
      t.integer :user_id   #fork用户的id
      t.timestamps
    end
    add_index :fork_users, :project_id
    add_index :fork_users, :user_id

    projects = Project.where("forked_from_project_id is not null")
    projects.each do |p|
      ForkUser.create(project_id: p.forked_from_project_id, fork_project_id: p.id, user_id: p.user_id)
    end
  end
end