php mysql游标

Question

我需要创建一个MySQL游标，以便在遍历一个“巨大”(数百万个实体)表时跟踪我当前要达到的行号。

样本数据库表：

CREATE TABLE  test (
id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY ,
someText TEenter code hereXT NOT NULL
) ;

如果此表为1,000,000项，则执行以下查询：

select * from test where id >= 50;

然后，根据我的php脚本中的需要处理数据(限制为1分钟)。如何跟踪已遍历"test“表的行？

Answer 1

// use a PHP session to store the id (could also use cookies...)
session_start();

// your 1 minute timeout
set_time_limit(60);

// query your results (may even put a known-out-of-reach limit on the
// query just to make sure you're not always pulling all the entries every
// reload (that would each up your timeout alone, depending)
$lastID = 0; // lowest possible ID value (e.g. MIN(id) )
if (session_is_registered('last_select_id'))
{
  $lastID =(int)$_SESSION['last_select_id'];
}
else
{
  session_register('last_select_id');
  $_SESSION['last_select_id'] = $lastID;
}
$dbResult = mysql_query("SELECT * FROM test WHERE id>{$lastID} ORDER BY id"/* LIMIT 10000 */);
if ($dbResult)
{
  while (($row = mysql_fetch_row($dbResult)) !== false)
  {
    // perform processing

    // mark as last processed (depending how many steps,
    // you may decide to move this from end to somewhere
    // else, just sh*t luck where your timeout occurs)
    $_SESSION['last_select_id'] = $row['id'];
  }
}

// it reached the end, save to assume we can remove the session variable
session_unregister('last_select_id');

我只能按你说的做，尽管我觉得这应该是本机的节流，而不仅仅是等待PHP吐出一个超时。

编辑的另一种方法，扩展了批处理思想，就是修改表并添加一个可以更新的“已处理”列。

EDIT2也要小心。我确实设置/取消了会话值。由于这个原因，如果您刷新了一个成功的页面加载，而不是一个超时错误( $lastID不会看到会话变量，它将在1重新启动，然后继续执行)，那么这个循环就会无限循环。