MongoDB 从集合中提取数组元素 [英] MongoDB pull array element from a collection

问题描述

我有一个 mongodb 对象如下:

I have a mongodb object as follows:

array (
  '_id' => new MongoId("4cc97fb0247ae8747ec5fefb"),
  'posts' => 
  array (
    0 => 
    array (
      'comment' => 'Eamorr',
      'fromUname' => 'Eamorr',
      'time' => 1288273840,
      'UTC' => '2010-10-28T14:50:40+01:00',
      'ip' => '127.0.0.1',
      'id' => '123lasdfiqwoei28asdf',
    ),
    1 => 
    array (
      'comment' => 'Hello',
      'fromUname' => 'Eamorr',
      'time' => 1288277023,
      'UTC' => '2010-10-28T15:43:43+01:00',
      'ip' => '127.0.0.1',
      'id' => 'qopqwier982389qwfa',
    ),
    2 => 
    array (
      'comment' => 'Hello',
      'fromUname' => 'Anonymous',
      'time' => 1288283506,
      'UTC' => '2010-10-28T17:31:46+01:00',
      'ip' => '127.0.0.1',
      'id' => 'ioqwoeias892398wrf',
    ),
    /////
    //Want to remove element 3:
    /////
    3 => 
    array (
      'comment' => 'asdfasadf',
      'fromUname' => 'Anonymous',
      'time' => 1288283864,
      'UTC' => '2010-10-28T17:37:44+01:00',
      'ip' => '127.0.0.1',
      'id' => 'wwwwwiasdfn234oiasf',
    ),
    4 => 
    array (
      'comment' => 'asdfasdfasdf',
      'fromUname' => 'Anonymous',
      'time' => 1288284076,
      'UTC' => '2010-10-28T17:41:16+01:00',
      'ip' => '127.0.0.1',
      'id' => '290qwefoiqweproiqwerpq',
    ),
    5 => 
    array (
      'comment' => 'ASDF',
      'fromUname' => 'Eamorr',
      'time' => 1288284331,
      'UTC' => '2010-10-28T17:45:31+01:00',
      'ip' => '127.0.0.1',
      'id' => 'eioqw8923892hasdf',
    ),
    6 => 
    array (
      'comment' => 'ASDF2',
      'fromUname' => 'Eamorr',
      'time' => 1288284370,
      'UTC' => '2010-10-28T17:46:10+01:00',
      'ip' => '127.0.0.1',
      'id' => '23oaiofsaij234',
    ),
  ),
  'uname' => 'Eamorr',
)

现在，我正在编写一些 PHP 代码来删除帖子 [x].我正在尝试使用 $pull 删除数组元素.

Now, I am writing some PHP code to remove posts[x]. I'm trying to use $pull to remove the array element.

我有一个 'id' 'wwwwwiasdfn234oiasf'(数组元素 3)，我想删除这个整个数组元素，只在 'posts' 数组中留下 6 个元素.

I have an 'id' 'wwwwwiasdfn234oiasf' (array element 3) and I want to remove this entire array element, leaving just 6 elements in the 'posts' array.

我试过谷歌搜索并查找文档无济于事......我仍然无法掌握 mongodb 语法.

I've tried googling and looking up the documentation to no avail... I still can't get the hang of the mongodb syntax.

我正在用 PHP 完成所有这些工作，但任何语言都可以，我应该能够进行翻译.

I'm doing all this in PHP, but any language will do I should be able to do the translation.

非常感谢，

解决方案(在 PHP 中):

Solution (in PHP):

$uname=whatever
$id=whatever
$mongo=new Mongo();
$walls=$mongo->people->walls;
$walls->update(array('uname'=>$uname),array('$pull'=>array('posts'=>array('id'=>$id))));

推荐答案

以下是使用 MongoDB shell 的方法.您应该可以将其翻译成 PHP.

Here's how to do it using the MongoDB shell. You should be able to translate it into PHP.

拉取操作由$pull修饰符、字段选择器和值表达式组成.

A pull operation consists of the $pull modifier, a field selector and a value expression.

{ $pull: { fieldSelector: valueExpression } }

在您的情况下，字段选择器是 posts，因为这是您要更新的数组.简单来说，值表达式是

In your case the field selector is posts, since that's the array you want to update. The value expression, in plain English, is

其中帖子的 id 等于wwwwwiasdfn234oiasf"

where the id of the post equals "wwwwwiasdfn234oiasf"

这转化为 { id: "wwwwwiasdfn234oiasf" }.如果我们将所有这些结合起来，您将得到以下 $pull 语句，它将从数组中删除所需的项目:

This translates to { id: "wwwwwiasdfn234oiasf" }. If we combine all of this, you'll get the following $pull statement, which will remove the desired item from the array:

{ $pull: { posts: { id: "wwwwwiasdfn234oiasf" } } }

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