The DB layer Writing a custom driver Metadata

The metadata part will describe the DB and what it can do. Let's take a look on RethinkDB:

<?php

/**
 * RethinkDB metadata handler.
 */
class RethinkDbMetadataHandler implements DbMetadataHandlerInterface {

  /**
   * {@inheritdoc}
   */
  public function dbType() {
    return 'NoSQL';
  }

  /**
   * {@inheritdoc}
   */
  public function installerDescription() {
    return 'No SQL light weight DB with real time support.';
  }

  /**
   * {@inheritdoc}
   */
  public function supportRealTime() {
    return TRUE;
  }

}

dbType(): What the DB type: A NoSQL or SQL.

installerDescription(): Small description on the DB. It will appear in the installation and provide to the user information about the DB and why the choose the DB as the daily driver.

supportRealTime(): One of nuntius commands allows you to see live changes in a table. For the command to work, the DB metadata need to tell if the DB support real time or not.