// No rows were seen by MAX
			return FromNull(), nil
		}
		return e.aggregate.runningMax, nil

	case aggFnSum:
		// TODO: check if returning 0 when no rows were seen
		// by SUM is expected behavior.
		return e.aggregate.runningSum, nil

	default:
		// TODO:
	}

	return nil, errInvalidAggregation