presto-main/src/main/java/io/prestosql/execution/SqlTaskExecution.java/DriverSplitRunner/processFor
class DriverSplitRunner:        @Override
        public ListenableFuture<?> processFor(Duration duration)
        {
            Driver driver;
            synchronized (this) {
                // if close() was called before we get here, there's not point in even creating the driver
                if (closed) {
                    return Futures.immediateFuture(null);
                }

                if (this.driver == null) {
                    this.driver = driverSplitRunnerFactory.createDriver(driverContext, partitionedSplit);
                }

                driver = this.driver;
            }

            return driver.processFor(duration);
        }