drupal7 分页

$output = "";

    $query = db_select('feedback','f')->extend('PagerDefault');//->extend('PagerDefault')不能少哦

    $query -> fields('f');

    $query->orderBy('f.created','DESC');

    $query -> limit(5);//每页记录数量
    $objects = $query -> execute() -> fetchAll();
    
    
    $type=1;
    $fb_limit = db_query("SELECT * FROM {feedback_config} WHERE type =  :type", array(':type'=>$type))->fetch();
   
    $rows = array(); 
    foreach ($objects as $key => $object) {
        $row = array();
        $row['fid'] = $object -> fid ; 
        //标题
        $row['title'] = $object->title <= $fb_limit->num_title_topshow?
          $object -> title:
          drupal_substr($object -> title,0,$fb_limit->num_title_topshow).'...' ;
        $row['full_title']=$object->title;
        //标题
        $row['body'] = $object -> body<=$fb_limit->num_body_topshow?
          $object -> body:
          drupal_substr($object -> body, 0,$fb_limit->num_body_topshow).'...' ;
        
        $row['created']=date('Y-m-d H:i:s',$object->created); 
        $rows[] = $row;
    }
    $output .= theme('hellozjf_top', array('rows' => $rows));


 $output .= theme('pager');//drupal7自带分页功能
    
  return $output;

 不要问我底层的实现原理，我也是不知道呢，暂时记一下~

效果：

很纳闷，单击2,3····页时，代码是怎么知道该怎么查询的？是把查询语句缓存了吗？