presto-main/src/main/java/io/prestosql/operator/WorkProcessorUtils.java/ProcessWorkProcessor/process
class ProcessWorkProcessor:        @Override
        public boolean process()
        {
            if (isBlocked()) {
                return false;
            }
            if (isFinished()) {
                return true;
            }
            state = requireNonNull(process.process());

            if (state.getType() == ProcessState.Type.FINISHED) {
                process = null;
                return true;
            }

            return state.getType() == ProcessState.Type.RESULT;
        }