Method PrepareForReadInternal

be/src/runtime/buffered-tuple-stream.cc:633–661

}

Status BufferedTupleStream::PrepareForReadInternal(
    bool attach_on_read, ReadIterator* read_iter) {
  DCHECK(!closed_);
  DCHECK(!read_it_.attach_on_read_);
  DCHECK(!read_iter->is_valid());

  read_iter->Init(attach_on_read);
  if (pages_.empty()) {
    // No rows to return, or a the first read/write page has not yet been allocated.
    read_iter->SetReadPage(pages_.end());
  } else {
    // Eagerly pin the first page in the stream.
    read_iter->SetReadPage(pages_.begin());
    if (read_iter == &read_it_ && !pinned_
        && read_iter->read_page_->len() > default_page_len_) {
      int64_t extra_needed_reservation = read_iter->read_page_->len() - default_page_len_;
      if (large_read_page_reservation_.GetReservation() >= extra_needed_reservation) {
        buffer_pool_client_->RestoreReservation(&large_read_page_reservation_,
            extra_needed_reservation);
      }
    }
    // Check if we need to increment the pin count of the read page.
    RETURN_IF_ERROR(PinPageIfNeeded(&*read_iter->read_page_, pinned_));
    DCHECK(read_iter->read_page_->is_pinned());
    RETURN_IF_ERROR(read_iter->InitReadPtrs());
  }
  CHECK_CONSISTENCY_FULL(*read_iter);
  return Status::OK();
}

Status BufferedTupleStream::PinStream(bool* pinned) {
  DCHECK(!closed_);