Issue #3119170 by tstoeckler, daffie: Optimize...

    if (!$this->tableExists($table)) {

      return FALSE;

    }

    // Fetch the 'indkey' column from 'pg_index' to figure out the order of the

    // primary key.

    // @todo Use 'array_position()' to be able to perform the ordering in SQL

    //   directly when 9.5 is the minimum  PostgreSQL version.

    $result = $this->connection->query("SELECT a.attname, i.indkey FROM pg_index i JOIN pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = ANY(i.indkey) WHERE i.indrelid = '{" . $table . "}'::regclass AND i.indisprimary")->fetchAllKeyed();

    if (!$result) {

      return [];

    }

    $order = explode(' ', reset($result));

    $columns = array_combine($order, array_keys($result));

    ksort($columns);

    return array_values($columns);

    return $this->connection->query("SELECT array_position(i.indkey, a.attnum) AS position, a.attname FROM pg_index i JOIN pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = ANY(i.indkey) WHERE i.indrelid = '{" . $table . "}'::regclass AND i.indisprimary ORDER BY position")->fetchAllKeyed();

  }

  /**