Method extractSerializedRows

bolt/exec/RowContainer.cpp:690–760

}

void RowContainer::extractSerializedRows(
    folly::Range<char**> rows,
    const VectorPtr& result) {
  // The format of the extracted row is: null bytes followed by keys and
  // dependent columns. Fixed-width columns are serialized into fixed number of
  // bytes (see typeKindSize). Variable-width columns are serialized as 4 bytes
  // of size followed by that many bytes.

  const int32_t nullBytes = bits::nbytes(nullOffsets_.size());

  // First, calculate total number of bytes needed to serialize all rows.

  size_t fixedWidthRowSize = 0;
  bool hasVariableWidth = false;
  for (auto i = 0; i < types_.size(); ++i) {
    const auto& type = types_[i];
    if (type->isFixedWidth()) {
      fixedWidthRowSize += typeKindSize(type->kind());
    } else {
      hasVariableWidth = true;
    }
  }

  size_t totalBytes = nullBytes * rows.size() + fixedWidthRowSize * rows.size();
  if (hasVariableWidth) {
    for (const char* row : rows) {
      for (auto i = 0; i < types_.size(); ++i) {
        const auto& type = types_[i];
        if (!type->isFixedWidth()) {
          // 4 bytes for size + N bytes for data.
          totalBytes += 4 + variableSizeAt(row, i);
        }
      }
    }
  }

  // Allocate sufficient buffer.
  auto* flatResult = result->as<FlatVector<StringView>>();
  flatResult->resize(rows.size());
  auto* rawBuffer = flatResult->getRawStringBufferWithSpace(totalBytes, true);

  // Write serialized data.
  size_t totalWritten = 0;
  for (auto i = 0; i < rows.size(); ++i) {
    auto* row = rows[i];
    size_t offset = 0;

    // Copy nulls.
    memcpy(rawBuffer + offset, row + rowColumns_[0].nullByte(), nullBytes);
    offset += nullBytes;

    // Copy values.
    for (auto j = 0; j < types_.size(); ++j) {
      const auto& type = types_[j];
      if (type->isFixedWidth()) {
        const auto size = typeKindSize(type->kind());
        memcpy(rawBuffer + offset, row + rowColumns_[j].offset(), size);
        offset += size;