MongoDB - 为什么我应该使用游标而不是iterator_to_array（在PHP中） [英] MongoDB - Why should I use a cursor instead of iterator_to_array (in PHP)

问题描述

mongo类的PHP文档说明使用光标的 iterator_to_array 是优越的。为什么？ 使用 iterator_to_array（） c>使您的驱动程序将所有结果一次性加载到内存中，您可能很容易耗尽内存。这不是使用延迟加载的游标的情况！

直接从链接的 docs ：

 <？php 
 
 $ cursor = $ collection-> find（）; 
 var_dump（iterator_to_array（$ cursor））; 
 
？> 
  

...

在上面的示例中， $ collection 是一个50GB的集合。我们当然不希望将它一次加载到内存中，这是一个游标：允许客户端访问dribs和drabs中的集合。

The PHP documentation for the mongo class says using a cursor instead of iterator_to_array is superior. Why? What benefits/flexibility will I get from that?

解决方案

Using iterator_to_array() makes your driver load all of the results into memory at once, and you could easily run out of memory. This would not be the case with a cursor, which uses lazy-loading!

Straight from the linked docs:

<?php

$cursor = $collection->find();
var_dump(iterator_to_array($cursor));

?>

...

Suppose that, in the example above, $collection was a 50GB collection. We certainly wouldn't want to load that into memory all at once, which is what a cursor is for: allowing the client to access the collection in dribs and drabs.

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