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class AddUniqueIndexOnMembers < ActiveRecord::Migration

  def self.up

    # Clean and reassign MemberRole rows if needed

    MemberRole.delete_all("member_id NOT IN (SELECT id FROM #{Member.table_name})")

    MemberRole.update_all("member_id =" +

      " (SELECT min(m2.id) FROM #{Member.table_name} m1, #{Member.table_name} m2" +

      " WHERE m1.user_id = m2.user_id AND m1.project_id = m2.project_id" +

      " AND m1.id = #{MemberRole.table_name}.member_id)")

    # Remove duplicates

    Member.connection.select_values("SELECT m.id FROM #{Member.table_name} m" +

      " WHERE m.id > (SELECT min(m1.id) FROM #{Member.table_name} m1 WHERE m1.user_id = m.user_id AND m1.project_id = m.project_id)").each do |i|

        Member.delete_all(["id = ?", i])

      end

    # Then add a unique index

    add_index :members, [:user_id, :project_id], :unique => true

  end

  def self.down

    remove_index :members, [:user_id, :project_id]

  end

end