presto-main/src/main/java/io/prestosql/execution/buffer/LazyOutputBuffer.java/LazyOutputBuffer/getUtilization
class LazyOutputBuffer:    @Override
    public double getUtilization()
    {
        OutputBuffer outputBuffer;
        synchronized (this) {
            outputBuffer = delegate;
        }

        // until output buffer is initialized, it is "full"
        if (outputBuffer == null) {
            return 1.0;
        }
        return outputBuffer.getUtilization();
    }