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https://github.com/ClickHouse/ClickHouse.git
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97f2a2213e
* Move some code outside dbms/src folder * Fix paths
159 lines
4.8 KiB
C++
159 lines
4.8 KiB
C++
#include <errno.h>
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#include <time.h>
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#include <optional>
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#include <Common/ProfileEvents.h>
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#include <Common/Stopwatch.h>
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#include <Common/Exception.h>
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#include <Common/CurrentMetrics.h>
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#include <IO/ReadBufferFromFileDescriptor.h>
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#include <IO/WriteHelpers.h>
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namespace ProfileEvents
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{
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extern const Event ReadBufferFromFileDescriptorRead;
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extern const Event ReadBufferFromFileDescriptorReadFailed;
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extern const Event ReadBufferFromFileDescriptorReadBytes;
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extern const Event DiskReadElapsedMicroseconds;
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extern const Event Seek;
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}
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namespace CurrentMetrics
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{
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extern const Metric Read;
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}
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int CANNOT_READ_FROM_FILE_DESCRIPTOR;
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extern const int ARGUMENT_OUT_OF_BOUND;
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extern const int CANNOT_SEEK_THROUGH_FILE;
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extern const int CANNOT_SELECT;
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}
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std::string ReadBufferFromFileDescriptor::getFileName() const
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{
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return "(fd = " + toString(fd) + ")";
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}
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bool ReadBufferFromFileDescriptor::nextImpl()
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{
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size_t bytes_read = 0;
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while (!bytes_read)
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{
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ProfileEvents::increment(ProfileEvents::ReadBufferFromFileDescriptorRead);
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Stopwatch watch(profile_callback ? clock_type : CLOCK_MONOTONIC);
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ssize_t res = 0;
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{
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CurrentMetrics::Increment metric_increment{CurrentMetrics::Read};
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res = ::read(fd, internal_buffer.begin(), internal_buffer.size());
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}
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if (!res)
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break;
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if (-1 == res && errno != EINTR)
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{
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ProfileEvents::increment(ProfileEvents::ReadBufferFromFileDescriptorReadFailed);
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throwFromErrnoWithPath("Cannot read from file " + getFileName(), getFileName(),
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ErrorCodes::CANNOT_READ_FROM_FILE_DESCRIPTOR);
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}
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if (res > 0)
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bytes_read += res;
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/// It reports real time spent including the time spent while thread was preempted doing nothing.
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/// And it is Ok for the purpose of this watch (it is used to lower the number of threads to read from tables).
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/// Sometimes it is better to use taskstats::blkio_delay_total, but it is quite expensive to get it (TaskStatsInfoGetter has about 500K RPS).
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watch.stop();
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ProfileEvents::increment(ProfileEvents::DiskReadElapsedMicroseconds, watch.elapsedMicroseconds());
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if (profile_callback)
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{
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ProfileInfo info;
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info.bytes_requested = internal_buffer.size();
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info.bytes_read = res;
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info.nanoseconds = watch.elapsed();
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profile_callback(info);
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}
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}
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pos_in_file += bytes_read;
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if (bytes_read)
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{
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ProfileEvents::increment(ProfileEvents::ReadBufferFromFileDescriptorReadBytes, bytes_read);
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working_buffer.resize(bytes_read);
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}
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else
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return false;
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return true;
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}
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/// If 'offset' is small enough to stay in buffer after seek, then true seek in file does not happen.
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off_t ReadBufferFromFileDescriptor::seek(off_t offset, int whence)
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{
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off_t new_pos;
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if (whence == SEEK_SET)
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new_pos = offset;
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else if (whence == SEEK_CUR)
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new_pos = pos_in_file - (working_buffer.end() - pos) + offset;
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else
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throw Exception("ReadBufferFromFileDescriptor::seek expects SEEK_SET or SEEK_CUR as whence", ErrorCodes::ARGUMENT_OUT_OF_BOUND);
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/// Position is unchanged.
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if (new_pos + (working_buffer.end() - pos) == pos_in_file)
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return new_pos;
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if (hasPendingData() && new_pos <= pos_in_file && new_pos >= pos_in_file - static_cast<off_t>(working_buffer.size()))
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{
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/// Position is still inside buffer.
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pos = working_buffer.begin() + (new_pos - (pos_in_file - working_buffer.size()));
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return new_pos;
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}
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else
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{
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ProfileEvents::increment(ProfileEvents::Seek);
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Stopwatch watch(profile_callback ? clock_type : CLOCK_MONOTONIC);
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pos = working_buffer.end();
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off_t res = ::lseek(fd, new_pos, SEEK_SET);
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if (-1 == res)
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throwFromErrnoWithPath("Cannot seek through file " + getFileName(), getFileName(),
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ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
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pos_in_file = new_pos;
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watch.stop();
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ProfileEvents::increment(ProfileEvents::DiskReadElapsedMicroseconds, watch.elapsedMicroseconds());
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return res;
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}
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}
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/// Assuming file descriptor supports 'select', check that we have data to read or wait until timeout.
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bool ReadBufferFromFileDescriptor::poll(size_t timeout_microseconds)
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{
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fd_set fds;
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FD_ZERO(&fds);
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FD_SET(fd, &fds);
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timeval timeout = { time_t(timeout_microseconds / 1000000), suseconds_t(timeout_microseconds % 1000000) };
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int res = select(1, &fds, nullptr, nullptr, &timeout);
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if (-1 == res)
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throwFromErrno("Cannot select", ErrorCodes::CANNOT_SELECT);
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return res > 0;
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}
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}
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