presto-main/src/main/java/io/prestosql/operator/OrderByOperator.java/OrderByOperator/startMemoryRevoke
class OrderByOperator:    @Override
    public ListenableFuture<?> startMemoryRevoke()
    {
        verify(state == State.NEEDS_INPUT || revocableMemoryContext.getBytes() == 0, "Cannot spill in state: %s", state);
        return spillToDisk();
    }