Method ScanBatchTask

cpp/src/arrow/dataset/scan_node.cc:212–223

  struct ScanBatchTask : public util::AsyncTaskScheduler::Task {
    ScanBatchTask(ScanNode* node, ScanState* scan_state, int batch_index)
        : node_(node), scan_(scan_state), batch_index_(batch_index) {
      int64_t cost = scan_state->fragment_scanner->EstimatedDataBytes(batch_index_);
      // It's possible, though probably a bad idea, for a single batch of a fragment
      // to be larger than 2GiB.  In that case, it doesn't matter much if we
      // underestimate because the largest the throttle can be is 2GiB and thus we will
      // be in "one batch at a time" mode anyways which is the best we can do in this
      // case.
      cost_ = static_cast<int>(
          std::min(cost, static_cast<int64_t>(std::numeric_limits<int>::max())));
      name_ = "ScanNode::ScanBatch::" + ::arrow::internal::ToChars(batch_index_);
    }

    Result<Future<>> operator()() override {
      // Prevent concurrent calls to ScanBatch which might not be thread safe