Function read_array_with_qc

examples/cpp_api/query_condition_sparse.cc:167–225

* @brief Executes the read query for the array created in write_array. * * @param ctx The context. * @param qc The query condition to execute the query with. */

 * @param qc The query condition to execute the query with.
 */
void read_array_with_qc(Context& ctx, std::optional<QueryCondition> qc) {
  // Create data buffers to read the values into.
  std::vector<int> a_data(num_elems);
  std::vector<uint8_t> a_data_validity(num_elems);

  // We initialize the string b_data to contain 44 characters because
  // that is the combined size of all strings in attribute b.
  std::string b_data;
  b_data.resize(44);

  std::vector<uint64_t> b_data_offsets(num_elems);
  std::vector<int32_t> c_data(num_elems);
  std::vector<float> d_data(num_elems);

  // Execute the read query.
  Array array(ctx, array_name, TILEDB_READ);
  Query query(ctx, array);
  query.set_layout(TILEDB_ROW_MAJOR)
      .set_data_buffer("a", a_data)
      .set_validity_buffer("a", a_data_validity)
      .set_data_buffer("b", b_data)
      .set_offsets_buffer("b", b_data_offsets)
      .set_data_buffer("c", c_data)
      .set_data_buffer("d", d_data);
  if (qc) {
    query.set_condition(qc.value());
  }
  query.submit();

  // Collect the results of the read query. The number of elements
  // the filtered array contains is in num_elements_result.
  // The length of the filtered substring of all the data is in
  // b_data, and all the offsets for filtered individual elements
  // are in  b_data_offsets.
  auto table = query.result_buffer_elements_nullable();
  size_t num_elements_result = std::get<1>(table["c"]);
  uint64_t b_str_length = std::get<1>(table["b"]);
  b_data_offsets.push_back(b_str_length);

  // Here we print all the elements that are returned by the query.
  for (size_t i = 0; i < num_elements_result; ++i) {
    // We pass in nullopt if the data is invalid, per the validity buffer.
    std::optional<int> a_val;
    if (a_data_validity[i]) {
      a_val = a_data[i];
    } else {
      a_val = std::nullopt;
    }
    print_elem(
        a_val,
        b_data.substr(
            b_data_offsets[i], b_data_offsets[i + 1] - b_data_offsets[i]),
        c_data[i],
        d_data[i]);
  }

  query.finalize();
  array.close();