moebooru/db/migrate/058_remove_notes_from_artists.rb

class RemoveNotesFromArtists < ActiveRecord::Migration[5.1]
  def self.up
    Artist.find(:all, conditions: [ "notes <> '' and notes is not null" ]).each do |artist|
      page = WikiPage.find_by_title(artist.name)
      notes = artist.__send__(:read_attribute, :notes)

      if page
        page.update(body: notes, ip_addr: "127.0.0.1", user_id: 1)
      else
        WikiPage.create(title: artist.name, body: notes, ip_addr: "127.0.0.1", user_id: 1)
      end
    end

    remove_column :artists, :notes
  end

  def self.down
    add_column :artists, :notes, :text, default: "", null: false
  end
end