我有一个目录,我使用下面的PHP脚本构建,它使用分页每页获得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.
我猜测我对查询做了一些错误,而不仅仅是选择1002结果它应该被限制,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"); ?>
在大多数数据库中,使用偏移的LIMIT非常慢(我已经找到了一些 针对MySQL的文档,我试图找到一篇非常好的文章,我刚才读过这篇文章,为SQLite解释这个).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这样做LIMIT 10000, 10,它将被解释为:
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,数据库仍需要遍历10,000个索引值,然后才能获得10个结果.可能有进一步的优化可以改善这一点,但在一般情况下,您不希望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,所以如果第一页结束id = 5,那么让你的下一个链接WHERE id > 5(LIMIT x当然有).
编辑:找到SQLite的文章.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人员非常聪明,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只记住显示中顶部条目的索引并运行如下查询:
Run Code Online (Sandbox Code Playgroud)SELECT title FROM tracks WHERE singer='Madonna' ORDER BY title LIMIT 5 OFFSET :index将索引初始化为0.要向下滚动,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.因此,例如,如果:index为1000,您实际上是在读取1005个条目并忽略除最后5个之外的所有条目.净效果是当您在列表中越来越低时滚动开始变得迟缓.