$data['vote']['table']['join'][$table] = array(
  'left_field' => 'pool',
  'field' => 'pool',
  'extra' => array(
    array(
      'field' => 'entity_type',
      'left_field' => 'entity_type',
      'operator' => '=',
    ),
    array(
      'field' => 'entity_id',
      'left_field' => 'entity_id',
      'operator' => '=',
    ),
  ),
);

$data[$table]['table']['join']['vote'] = array(
  'left_field' => 'pool',
  'field' => 'pool',
  'extra' => array(
    array(
      'field' => 'entity_type',
      'left_field' => 'entity_type',
      'operator' => '=',
    ),
    array(
      'field' => 'entity_id',
      'left_field' => 'entity_id',
      'operator' => '=',
    ),
  ),
);