presto-main/src/main/java/io/prestosql/execution/buffer/ArbitraryOutputBuffer.java/ArbitraryOutputBuffer/noMoreBuffers
class ArbitraryOutputBuffer:    private synchronized void noMoreBuffers()
    {
        if (outputBuffers.isNoMoreBufferIds()) {
            // verify all created buffers have been declared
            SetView<OutputBufferId> undeclaredCreatedBuffers = Sets.difference(buffers.keySet(), outputBuffers.getBuffers().keySet());
            checkState(undeclaredCreatedBuffers.isEmpty(), "Final output buffers does not contain all created buffer ids: %s", undeclaredCreatedBuffers);
        }
    }