Method TryReadFromCache

be/src/runtime/io/request-context.cc:538–565

}

Status RequestContext::TryReadFromCache(const unique_lock<mutex>& lock,
    ScanRange* range, bool* read_succeeded, bool* needs_buffers) {
  DCHECK(lock.mutex() == &lock_ && lock.owns_lock());
  RETURN_IF_ERROR(range->ReadFromCache(lock, read_succeeded));
  if (!*read_succeeded) return Status::OK();

  DCHECK(Validate()) << endl << DebugString();
  // The following cases are possible at this point:
  // * The scan range doesn't have sub-ranges:
  // ** 'range->buffer_manager_->buffer_tag' is CACHED_BUFFER and the buffer is
  //    already available to the reader.
  //    (there is nothing to do)
  //
  // * The scan range has sub-ranges, and 'range->buffer_manager_->buffer_tag' is:
  // ** INTERNAL_BUFFER: the client needs to add buffers to the scan range.
  // ** CLIENT_BUFFER: the client already provided a buffer to copy data into it.
  *needs_buffers = range->buffer_manager_->is_internal_buffer();
  if (*needs_buffers) {
    DCHECK(range->HasSubRanges());
    range->SetBlockedOnBuffer();
    // The range will be scheduled when buffers are added to it.
    AddRangeToDisk(lock, range, ScheduleMode::BY_CALLER);
  } else if (range->buffer_manager_->is_client_buffer()) {
    DCHECK(range->HasSubRanges());
    AddRangeToDisk(lock, range, ScheduleMode::IMMEDIATELY);
  }
  return Status::OK();
}

Status RequestContext::AddWriteRange(WriteRange* write_range) {
  unique_lock<mutex> lock(lock_);