std::unique_ptr ColumnReader::build()

in velox/dwio/dwrf/reader/ColumnReader.cpp [2089:2175]
87 lines of code
20 McCabe index (conditional complexity)

std::unique_ptr<ColumnReader> ColumnReader::build(
    const std::shared_ptr<const dwio::common::TypeWithId>& requestedType,
    const std::shared_ptr<const dwio::common::TypeWithId>& dataType,
    StripeStreams& stripe,
    FlatMapContext flatMapContext) {
  CompatChecker::check(*dataType->type, *requestedType->type);
  EncodingKey ek{dataType->id, flatMapContext.sequence};
  switch (dataType->type->kind()) {
    case TypeKind::INTEGER:
      return buildIntegerReader(
          dataType,
          requestedType->type->kind(),
          INT_BYTE_SIZE,
          std::move(flatMapContext),
          stripe);
    case TypeKind::BIGINT:
      return buildIntegerReader(
          dataType,
          requestedType->type->kind(),
          LONG_BYTE_SIZE,
          std::move(flatMapContext),
          stripe);
    case TypeKind::SMALLINT:
      return buildIntegerReader(
          dataType,
          requestedType->type->kind(),
          SHORT_BYTE_SIZE,
          std::move(flatMapContext),
          stripe);
    case TypeKind::VARBINARY:
    case TypeKind::VARCHAR:
      switch (static_cast<int64_t>(stripe.getEncoding(ek).kind())) {
        case proto::ColumnEncoding_Kind_DICTIONARY:
        case proto::ColumnEncoding_Kind_DICTIONARY_V2:
          return std::make_unique<StringDictionaryColumnReader>(
              dataType, stripe, std::move(flatMapContext));
        case proto::ColumnEncoding_Kind_DIRECT:
        case proto::ColumnEncoding_Kind_DIRECT_V2:
          return std::make_unique<StringDirectColumnReader>(
              dataType, stripe, std::move(flatMapContext));
        default:
          DWIO_RAISE("buildReader unhandled string encoding");
      }
    case TypeKind::BOOLEAN:
      return buildByteRleColumnReader<bool>(
          dataType,
          requestedType->type->kind(),
          stripe,
          std::move(flatMapContext));
    case TypeKind::TINYINT:
      return buildByteRleColumnReader<int8_t>(
          dataType,
          requestedType->type->kind(),
          stripe,
          std::move(flatMapContext));
    case TypeKind::ARRAY:
      return std::make_unique<ListColumnReader>(
          requestedType, dataType, stripe, std::move(flatMapContext));
    case TypeKind::MAP:
      if (stripe.getEncoding(ek).kind() ==
          proto::ColumnEncoding_Kind_MAP_FLAT) {
        return FlatMapColumnReaderFactory::create(
            requestedType, dataType, stripe, std::move(flatMapContext));
      }
      return std::make_unique<MapColumnReader>(
          requestedType, dataType, stripe, std::move(flatMapContext));
    case TypeKind::ROW:
      return std::make_unique<StructColumnReader>(
          requestedType, dataType, stripe, std::move(flatMapContext));
    case TypeKind::REAL:
      if (requestedType->type->kind() == TypeKind::REAL) {
        return std::make_unique<FloatingPointColumnReader<float, float>>(
            dataType, stripe, std::move(flatMapContext));
      } else {
        return std::make_unique<FloatingPointColumnReader<float, double>>(
            dataType, stripe, std::move(flatMapContext));
      }
    case TypeKind::DOUBLE:
      return std::make_unique<FloatingPointColumnReader<double, double>>(
          dataType, stripe, std::move(flatMapContext));
    case TypeKind::TIMESTAMP:
      return std::make_unique<TimestampColumnReader>(
          dataType, stripe, std::move(flatMapContext));
    default:
      DWIO_RAISE("buildReader unhandled type");
  }
}