public function getPrimaryKeys()
    {
        if ($this->primary_keys === null) {
            try {
                $this->primary_keys = $this->tableManager->metadata()->getPrimaryKeys($this->prefixed_table);
            } catch (\Soluble\Schema\Exception\NoPrimaryKeyException $e) {
                throw new Exception\PrimaryKeyNotFoundException(__METHOD__ . ': ' . $e->getMessage());
            //@codeCoverageIgnoreStart
            } catch (\Soluble\Schema\Exception\ExceptionInterface $e) {
                throw new Exception\RuntimeException(__METHOD__ . ": Cannot determine primary key on table " . $this->prefixed_table);
            }
            //@codeCoverageIgnoreEnd
        }
        return $this->primary_keys;
    }