Function main

bolt/examples/VectorReaderWriter.cpp:52–167

} // namespace

int main() {
  const int num_rows = 8;
  memory::MemoryManager::initialize(memory::MemoryManager::Options{});

  /****************** Vector Writer **********************/

  // Define rows to write
  SelectivityVector rows{num_rows};
  // Array<Map<int,int>>
  auto type = TypeFactory<TypeKind::ARRAY>::create(
      TypeFactory<TypeKind::MAP>::create(BIGINT(), BIGINT()));
  auto pool = memory::memoryManager()->addLeafPool();

  // result vector
  VectorPtr result;

  // 1. Make sure result is writable for rows of interest
  BaseVector::ensureWritable(rows, type, pool.get(), result);

  // 2. Define a vector writer VectorWriter<T> where T is the type expressed in
  // the simple function type system.
  exec::VectorWriter<Array<Map<int64_t, int64_t>>> vectorWriter;

  // 3. Initialize the writer to write to result vector.
  vectorWriter.init(*result->as<ArrayVector>());

  rows.applyToSelected([&](vector_size_t row) {
    // 4. To write to a specific row call setOffset(row) followed by current()
    // to get the writer at that row
    vectorWriter.setOffset(row);
    auto& arrayWriter = vectorWriter.current();

    // Insert a map element to the array
    auto& child = arrayWriter.add_item();

    // Insert 2 kv pairs to the map
    child.emplace(serial(), serial());
    child.emplace(serial(), serial());

    // Insert an empty map
    arrayWriter.add_item();

    // 5. After finishing writing the row call commit(), or commit(false) to
    // write a null
    vectorWriter.commit();
  });

  // 6. After finishing writing all rows, call finish()
  vectorWriter.finish();

  /****************** Vector Reader **********************/

  // 1. Decode the vector for rows of interest.
  DecodedVector decoded;
  decoded.decode(*result, rows);

  // 2. Define vectorReader<T> where T is the type of the vector being read, T
  // is expressed in the simple function type system