Retrieve results directly from index

Example with fields returned from a search view:

/**
   * Get AI Search view display fields.
   *
   * @param \Drupal\search_api\Query\QueryInterface $query
   *   The Search API query.
   *
   * @return array[]
   *   The fields array or an empty array.
   */
  private function getSearchAiViewFields(QueryInterface $query) {
    $tags = $query->getTags();
    if (in_array('views_ai_search', $tags)) {
      /** @var \Drupal\views\Entity\View */
      $view = $this->entityTypeManager->getStorage('view')->load('ai_search');
      if ($view) {
        $display = $view->getDisplay('default');
        if ($display && isset($display['display_options']['fields'])) {
          return $display['display_options']['fields'];
        }
      }
    }
    return [];
  }

  /**
   * Set field and values for search API item.
   *
   * @param \Drupal\search_api\IndexInterface $index
   *   The search api index.
   * @param \Drupal\search_api\Item\ItemInterface $item
   *   The search api item.
   * @param \Drupal\search_api\Item\FieldInterface $field
   *   The search api field.
   * @param mixed $value
   *   The field value.
   * @param string $field_id
   *   The field id.
   */
  private function setItemField(IndexInterface $index, ItemInterface $item, FieldInterface $field, $value, $field_id) {
    $datasource_id = $field->getDatasourceId();
    $property_path = $field->getPropertyPath();
    $node_definitions = $index->getPropertyDefinitions($datasource_id);
    if (isset($node_definitions[$property_path])) {
      $search_api_field = $this->fieldsHelper
        ->createFieldFromProperty(
          $index,
          $node_definitions[$property_path],
          $datasource_id,
          $property_path,
          $field_id,
          $field->getType()
        );
      $search_api_field->setValues([$value]);
      $item->setField($field_id, $search_api_field);
    }
  }

  /**
   * Implements hook_search_api_aais_query_params_alter().
   */
  #[Hook('search_api_aais_query_params_alter')]
  public function aaisQueryParamsAlter(QueryInterface $query, &$params) {
    // Add view fields to select header to return indexed values.
    $fields = $this->getSearchAiViewFields($query);
    foreach ($fields as $field) {
      $params['select'] .= ",{$field['id']}";
    }
  }

  /**
   * Implements hook_search_api_aais_query_results_alter().
   */
  #[Hook('search_api_aais_query_results_alter')]
  public function aaisQueryResultsAlter(QueryInterface $query, ResponseDataInterface $response) {
    // Get query results and results returned from Azure.
    $result_set = $query->getResults();
    $response_results = $response->getBody();
    $fields = $this->getSearchAiViewFields($query);
    if ($result_set->getResultCount() && $fields) {
      // Get index, result items, and index fields.
      $index = $query->getIndex();
      $results = $result_set->getResultItems();
      $index_fields = $index->getFields();
      foreach ($response_results['value'] as $response_result) {
        // Try to find a matching field for each response field and populate.
        $item = $results[$response_result['itemId']];
        foreach ($fields as $field) {
          $field_id = $field['id'];
          if (isset($response_result[$field_id]) && isset($index_fields[$field_id])) {
            $index_field = $index_fields[$field_id];
            $this->setItemField($index, $item, $index_field, $response_result[$field_id], $field_id);
          }
        }
      }
    }
  }

Hi Kieran,

Thanks for taking this on! Really appreciate it.

Tested and it seems to work great, I set a debug point in SearchApiFieldTrait to confirm entity loading was being skipped.

One caveat I am leaving for anyone that encounters this issue in the future, if you have entity IDs with this solution you need to set them to integer rather than string or you will encounter an error with views if some items do not have values (TypeError: round(): Argument #1 ($num) must be of type int|float, string given in round() (line 173 of /app/docroot/core/modules/views/src/Plugin/views/field/NumericField.php)). I had not noticed this until adding the patch because my workaround was skipping reference fields.

I left some very minor suggestions for improvement in an MR that I tested as well. Once you get a chance to review those, I will move this forward.