PHP PDO缓冲查询问题 [英] PHP PDO Buffered query problem

问题描述

我在使用PHP数据对象函数时遇到了一些严重的问题.我正在尝试使用缓冲查询循环遍历可观的结果集(约60k行，约1gig)，以避免获取整个结果集.

I'm having some serious problems with the PHP Data Object functions. I'm trying to loop through a sizeable result set (~60k rows, ~1gig) using a buffered query to avoid fetching the whole set.

无论我做什么，脚本都只是挂在PDO :: query()上-看来查询正在无缓冲运行(为什么结果集大小的更改会解决"问题?).这是我的代码来重现该问题:

No matter what I do, the script just hangs on the PDO::query() - it seems the query is running unbuffered (why else would the change in result set size 'fix' the issue?). Here is my code to reproduce the problem:

<?php
$Database = new PDO(
    'mysql:host=localhost;port=3306;dbname=mydatabase',
    'root',
    '',
    array(
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true
    )
);

$rQuery = $Database->query('SELECT id FROM mytable');

// This is never reached because the result set is too large
echo 'Made it through.';

foreach($rQuery as $aRow) {
    print_r($aRow);
}
?>

如果我将查询限制在合理的范围内，则可以正常运行:

If I limit the query with some reasonable number, it works fine:

$rQuery = $Database->query('SELECT id FROM mytable LIMIT 10');

我尝试使用PDO :: MYSQL_ATTR_MAX_BUFFER_SIZE并使用PDO :: prepare()和PDO :: execute()(尽管上面的查询中没有参数)，但都无济于事.任何帮助将不胜感激.

I have tried playing with PDO::MYSQL_ATTR_MAX_BUFFER_SIZE and using the PDO::prepare() and PDO::execute() as well (though there are no parameters in the above query), both to no avail. Any help would be appreciated.

推荐答案

如果我理解此权利，则缓冲查询涉及告诉PHP您要在开始处理之前等待整个结果集.在PDO之前，这是默认设置，您必须调用 ，如果您想立即处理结果.

If I understand this right, buffered queries involve telling PHP that you want to wait for the entire result set before you begin processing. Prior to PDO, this was the default and you had to call mysql_unbuffered_query if you wanted to deal with results immediately.

我不知道为什么PDO MySQL驱动程序页面上没有对此进行解释.

Why this isn't explained on the PDO MySQL driver page, I don't know.

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