-- One guess assignment per user per slot pair per symbol (top-half assets).

ALTER TABLE market_history_prospective_assignments
  DROP CONSTRAINT IF EXISTS market_history_prospective_as_assigned_user_id_older_slot_s_key;

ALTER TABLE market_history_prospective_assignments
  DROP CONSTRAINT IF EXISTS market_history_prospective_assignments_assigned_user_id_older_slot_s_key;

ALTER TABLE market_history_prospective_assignments
  DROP CONSTRAINT IF EXISTS market_history_prospective_assignments_user_slot_symbol_key;

ALTER TABLE market_history_prospective_assignments
  ADD CONSTRAINT market_history_prospective_assignments_user_slot_symbol_key
  UNIQUE (assigned_user_id, older_slot_start, newer_slot_start, symbol);