Database select extenders are converted to PSR-0

The select extenders allow manipulation of the initial select query. PagerSelectExtender and TableSortExtender are two which were renamed in Drupal 8.

Drupal 7

// Search query select extender
$query = db_select('search_index', 'i')
  ->extend('SearchQuery');

// Table sort select extender
$query = db_select('accesslog', 'a', array('target' => 'slave'))
  ->extend('TableSort');

// Pager select extender
$query = db_select('comment', 'c')
  ->extend('PagerDefault');

Drupal 8

// Search query select extender
$query = db_select('search_index', 'i')
  ->extend('Drupal\search\SearchQuery');

// Table sort select extender
$query = db_select('accesslog', 'a', array('target' => 'slave'))
   ->extend('Drupal\Core\Database\Query\TableSortExtender');

// Pager select extender
$query = db_select('comment', 'c')
  ->extend('Drupal\Core\Database\Query\PagerSelectExtender');