我有一个使用以下PHP脚本构建的目录,该目录使用分页来获取每页1002个结果。问题在于,您进入页面的距离越远,加载页面所需的时间就越长。例如,第1页的加载速度明显快于10,000页。
我猜我在查询中做错了什么,而不仅仅是选择应限制的1002个结果,它还循环遍历了之前的所有结果。如果有人可以发布需要修复的代码,那就太好了!
感谢您的时间和帮助!
<?php include("websites/header.html"); ?> <center> <?php /* Place code to connect to your DB here. */ include('websites/database.php'); // include your code to connect to DB. $tbl_name="list"; //your table name // How many adjacent pages should be shown on each side? $adjacents = 5; /* First get total number of rows in data table. If you have a WHERE clause in your query, make sure you mirror it here. */ $query = "SELECT COUNT(*) as num FROM $tbl_name"; $total_pages = mysql_fetch_array(mysql_query($query)); $total_pages = $total_pages[num]; /* Setup vars for query. */ $targetpage = "websites.php"; //your file name (the name of this file) $limit = 1002; //how many items to show per page $page = $_GET['page']; if($page) $start = ($page - 1) * $limit; //first item to display on this page else $start = 0; //if no page var is given, set start to 0 /* Get data. */ $sql = "SELECT website FROM $tbl_name LIMIT $start, $limit"; $result = mysql_query($sql); /* Setup page vars for display. */ if ($page == 0) $page = 1; //if no page var is given, default to 1. $prev = $page - 1; //previous page is page - 1 $next = $page + 1; //next page is page + 1 $lastpage = ceil($total_pages/$limit); //lastpage is = total pages / items per page, rounded up. $lpm1 = $lastpage - 1; //last page minus 1 /* Now we apply our rules and draw the pagination object. We're actually saving the code to a variable in case we want to draw it more than once. */ $pagination = ""; if($lastpage > 1) { $pagination .= "<div class=\"pagination2\">"; //previous button if ($page > 1) $pagination.= "<a href=\"$targetpage?page=$prev\">< previous</a>"; else $pagination.= "<span class=\"disabled\">< previous</span>"; //pages if ($lastpage < 7 + ($adjacents * 2)) //not enough pages to bother breaking it up { for ($counter = 1; $counter <= $lastpage; $counter++) { if ($counter == $page) $pagination.= "<span class=\"current\">$counter</span>"; else $pagination.= "<a href=\"$targetpage?page=$counter\">$counter</a>"; } } elseif($lastpage > 5 + ($adjacents * 2)) //enough pages to hide some { //close to beginning; only hide later pages if($page < 1 + ($adjacents * 2)) { for ($counter = 1; $counter < 4 + ($adjacents * 2); $counter++) { if ($counter == $page) $pagination.= "<span class=\"current\">$counter</span>"; else $pagination.= "<a href=\"$targetpage?page=$counter\">$counter</a>"; } $pagination.= "..."; $pagination.= "<a href=\"$targetpage?page=$lpm1\">$lpm1</a>"; $pagination.= "<a href=\"$targetpage?page=$lastpage\">$lastpage</a>"; } //in middle; hide some front and some back elseif($lastpage - ($adjacents * 2) > $page && $page > ($adjacents * 2)) { $pagination.= "<a href=\"$targetpage?page=1\">1</a>"; $pagination.= "<a href=\"$targetpage?page=2\">2</a>"; $pagination.= "..."; for ($counter = $page - $adjacents; $counter <= $page + $adjacents; $counter++) { if ($counter == $page) $pagination.= "<span class=\"current\">$counter</span>"; else $pagination.= "<a href=\"$targetpage?page=$counter\">$counter</a>"; } $pagination.= "..."; $pagination.= "<a href=\"$targetpage?page=$lpm1\">$lpm1</a>"; $pagination.= "<a href=\"$targetpage?page=$lastpage\">$lastpage</a>"; } //close to end; only hide early pages else { $pagination.= "<a href=\"$targetpage?page=1\">1</a>"; $pagination.= "<a href=\"$targetpage?page=2\">2</a>"; $pagination.= "..."; for ($counter = $lastpage - (2 + ($adjacents * 2)); $counter <= $lastpage; $counter++) { if ($counter == $page) $pagination.= "<span class=\"current\">$counter</span>"; else $pagination.= "<a href=\"$targetpage?page=$counter\">$counter</a>"; } } } //next button if ($page < $counter - 1) $pagination.= "<a href=\"$targetpage?page=$next\">next ></a>"; else $pagination.= "<span class=\"disabled\">next ></span>"; $pagination.= "</div>\n"; } ?> <?php $i = 0; echo '<table style="table-layout:fixed; width:1050px;"><tr>'; while($row = mysql_fetch_array($result)) { $i ++; if ($i<=3) { echo '<td style="word-wrap: break-word;"> <div><a href="http://www.mywebsite.com/check.php?site='.strtolower($row[website]).'">'.strtolower($row[website]).'</a></div> </td>'; } else { echo '</tr><tr>'; echo '<td style="word-wrap: break-word;"><div><a href="http://www.mywebsite.com/check.php?site='.strtolower($row[website]).'">'.strtolower($row[website]).'</a></div></td>'; $i = 0; $i++; } } echo '</tr></table>'; ?> <?=$pagination?> </center> <?php include("websites/footer.html"); ?>
在大多数数据库中,带有偏移量的LIMIT极其慢(我已经找到了一些 有关MySQL的文档,并且我试图找到我之前读过的关于SQLite的一篇很好的文章)。原因是通常已实现了以下内容:
LIMIT
如果您这样做LIMIT 10000, 10,这意味着什么,它将被解释为:
LIMIT 10000, 10
有一个微不足道的优化方法,因为您不关心它们的值,所以您至少可以对前10,000个结果使用索引,但是即使在那种情况下,数据库仍然需要遍历10,000个索引值才能给您10个结果。可能还有进一步的优化可以改善这一点,但是通常情况下, 您不想LIMIT对大值使用偏移量。
我知道,处理分页的最有效方法是跟踪最后一个索引,因此,如果第一个页面以结尾id = 5,则使您的 下一个 链接具有WHERE id > 5(LIMIT x当然带有)。
id = 5
WHERE id > 5
LIMIT x
编辑:找到了SQLite的文章。我强烈建议您阅读此书,因为它解释了在SQL中执行操作的正确方法。由于SQLite的人 真的很聪明, 而其他数据库也有同样的问题,因此我认为MySQL以类似的方式实现了这一点。
经常出现的另一个错误是程序员尝试使用LIMIT和OFFSET实现滚动窗口。这里的想法是,您首先只需要记住显示中顶部条目的索引,然后运行如下查询: SELECT title FROM tracks WHERE singer='Madonna' ORDER BY title LIMIT 5 OFFSET :index 索引初始化为0。要向下滚动,只需将索引增加5并重新运行查询即可。要向上滚动,请将索引递减5并重新运行。 以上将实际工作。 问题是当索引变大时它变慢。 OFFSET在SQLite中的工作方式是使sqlite3_step()函数忽略它看到的第一个:index断点。因此,例如,如果:index为1000,则您实际上是在读1005个条目,而忽略除最后5个之外的所有条目。最终的结果是,随着列表中的位置越来越低,滚动开始变得缓慢。
经常出现的另一个错误是程序员尝试使用LIMIT和OFFSET实现滚动窗口。这里的想法是,您首先只需要记住显示中顶部条目的索引,然后运行如下查询:
SELECT title FROM tracks WHERE singer='Madonna' ORDER BY title LIMIT 5 OFFSET :index
索引初始化为0。要向下滚动,只需将索引增加5并重新运行查询即可。要向上滚动,请将索引递减5并重新运行。
以上将实际工作。 问题是当索引变大时它变慢。 OFFSET在SQLite中的工作方式是使sqlite3_step()函数忽略它看到的第一个:index断点。因此,例如,如果:index为1000,则您实际上是在读1005个条目,而忽略除最后5个之外的所有条目。最终的结果是,随着列表中的位置越来越低,滚动开始变得缓慢。