class DraftSequence < ActiveRecord::Base def self.next!(user, key) user_id = user user_id = user.id unless user.is_a?(Integer) return 0 if user_id < 0 h = { user_id: user_id, draft_key: key } c = DraftSequence.find_by(h) c ||= DraftSequence.new(h) c.sequence ||= 0 c.sequence += 1 c.save! DB.exec("DELETE FROM drafts WHERE user_id = :user_id AND draft_key = :draft_key AND sequence < :sequence", draft_key: key, user_id: user_id, sequence: c.sequence) c.sequence end def self.current(user, key) return nil unless user user_id = user user_id = user.id unless user.is_a?(Integer) # perf critical path r, _ = DB.query_single('select sequence from draft_sequences where user_id = ? and draft_key = ?', user_id, key) r.to_i end end # == Schema Information # # Table name: draft_sequences # # id :integer not null, primary key # user_id :integer not null # draft_key :string not null # sequence :integer not null # # Indexes # # index_draft_sequences_on_user_id_and_draft_key (user_id,draft_key) UNIQUE #