我有一个使用下面的PHP脚本构建的目录，它使用分页来获得每页1002个结果。问题是你进入页面的距离越远，他们加载的时间就越长。例如，第1页的加载速度明显快于第10,000页。
我猜我在查询中做错了，而不仅仅选择了应该限制的1002结果，它也会循环遍历它之前的所有结果。如果有人可以发布需要修复的代码，那就太棒了！
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"); ?>
答案 0 :(得分：5)
在大多数数据库中，使用偏移的LIMIT非常慢（我发现some documentation对于MySQL的这种影响我正在尝试找到一篇非常好的文章，我刚才读了解释这适用于SQLite）。原因是它通常实现如下：
LIMIT子句不存在一样这意味着如果你LIMIT 10000, 10，那将被解释为：
有一个简单的优化，您至少可以使用索引获得前10,000个结果，因为您不关心它们的值，但即使在这种情况下，数据库仍然需要遍历10,000个索引值才能提供给您10个结果。可能有进一步优化可以改善这一点，但在一般情况下您不希望使用带有大值偏移量的LIMIT 。
我知道处理分页的最有效方法是跟踪最后一个索引，因此如果第一页在id = 5结束，那么请将下一个链接设为WHERE id > 5（当然LIMIT x）。
编辑：找到article for SQLite。我强烈建议您阅读本文，因为它解释了The Right Way™在SQL中做的事情。由于SQLite人员非常智能而其他数据库也存在同样的问题，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试图使用LIMIT和OFFSET实现滚动窗口。这里的想法是你首先记住显示中顶部条目的索引并运行如下查询：
SELECT title FROM tracks WHERE singer='Madonna' ORDER BY title LIMIT 5 OFFSET :index索引初始化为0.向下滚动只需将索引递增5并重新运行查询。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会变慢。 OFFSET在SQLite中的工作方式是它导致sqlite3_step（）函数忽略它看到的第一个：索引断点。所以，例如，如果：index是1000，你实际上是在读取1005个条目而忽略除了最后5个以外的所有条目。净效果是滚动开始变得缓慢，因为你在列表中越来越低。