Drupal table with pager from db_select()

drupal_table_pager.php

<?php
/**
 * Display point award report.
 *
 * Generates a list of awarded points.
 *
 * @return array $content
 */
function game_report_page_points() {
  $header = array(
    'id' => array('data' => t('ID'), 'field' => 'id'),
    'points' => array('data' => t('Points'), 'field' => 'points'),
    'point_name' => array('data' => t('Type'), 'field' => 'point_name'),
    'point_category' => array('data' => t('Category'), 'field' => 'point_category'),
    'timestamp' => array('data' => t('Date'), 'field' => 'timestamp'),
    'meta' => array('data' => t('Meta'), 'field' => 'meta'),
    'name' => array('data' => t('User'), 'field' => 'name'),
  );

  // For some mysterious reason only parts of the db_select API is chainable.
  // Which means that sometimes you have to split it up like I've done below.
  $query = db_select('game_points', 'p')
   ->extend('PagerDefault')
   ->extend('TableSort')
   ->limit(50)
   ->orderByHeader($header);

  $query->join('users', 'u', 'p.uid = u.uid');

  $query->fields('p', array(
      'id',
      'points',
      'point_name',
      'point_category',
      'timestamp',
      'meta',
    ));
  $query->fields('u', array('name'));

  $result = $query->execute()->fetchAllAssoc('id');

  $render = array(
    'table' => array(
      '#theme' => 'table',
      '#header' => $header,
      '#rows' => array_map(function ($row) {
        return (array)$row;
      }, $result),
      '#sticky' => TRUE,
      '#empty' => t('No points recorded yet.'),
    ),
    'pager' => array(
      '#theme' => 'pager',
    ),
  );

  _game_preprocess_report($render);

  return $render;
}

/**
 * Preproccsing of report tables.
 *
 * @param array $report
 *
 * @return void
 */
function _game_preprocess_report(&$report) {
  // Format dates, can someone tell me how to do this directly in the
  // query?
  foreach ($report['table']['#rows'] as $key => $row) {
    $time = $row['timestamp'];
    $row['timestamp'] = date('Y-m-d H:i:s', $time);
    $report['table']['#rows'][$key] = $row;
  }
}