public function load($index)
    {
        // Minor optimization, avoid lookups for unknow indexes
        if (!$this->exists($index)) {
            return;
        }

        // Can be null if index does not exists
        if (array_key_exists($index, $this->indexDefinitionCache)) {
            return $this->indexDefinitionCache[$index];
        }

        $param = $this
            ->db
            ->query(
                "SELECT data FROM {ucms_search_index} WHERE index_key = :index",
                ['index' => $index]
            )
            ->fetchField()
        ;

        if ($param) {
          $param = unserialize($param);
        }

        return $this->indexDefinitionCache[$index] = $param;
    }