Method readPrefix

src/DataStreams/IBlockInputStream.cpp:129–159

void IBlockInputStream::readPrefix()
{
#ifndef NDEBUG
    if (!read_prefix_is_called)
        read_prefix_is_called = true;
    else
        throw Exception("readPrefix is called twice for " + getName() + " stream", ErrorCodes::LOGICAL_ERROR);
#endif

    if (!info.started)
    {
        info.total_stopwatch.start();
        info.cpu_thread_stopwatch.start();
        info.started = true;
    }
    /// start of read
    UInt64 start_ns = info.total_stopwatch.elapsed();
    UInt64 start_cpu_ns = info.cpu_thread_stopwatch.elapsed();

    readPrefixImpl();

    forEachChild([&] (IBlockInputStream & child)
    {
        child.readPrefix();
        return false;
    });

    /// end of read, update wall time and cpu thread time of current stream
    info.wall_time_ns += info.total_stopwatch.elapsed() - start_ns;
    info.cpu_time_ns += info.cpu_thread_stopwatch.elapsed() - start_cpu_ns;
}


void IBlockInputStream::readSuffix()