在 MongoDB 文档中查找匹配的数组项
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Find matching array items in MongoDB document
提问by Jonathan Clark
I am developing a web app using Codeigniter and MongoDB. In the database I got a document that look like this:
我正在使用 Codeigniter 和 MongoDB 开发 Web 应用程序。在数据库中，我得到了一个如下所示的文档：
{
"_id": {
"$id": "4f609932615a935c18r000000"
},
"basic": {
"name": "The project"
},
"members": [
{
"user_name": "john",
"role": "user",
"created_at": {
"sec": 1331730738,
"usec": 810000
}
},
{
"user_name": "markus",
"role": "user",
"created_at": {
"sec": 1331730738,
"usec": 810000
}
}
]
}
I need to search this document using both user_name and role. Right now when I am using the below code I get both. I only want to get array items matching both user_name and role.
我需要使用 user_name 和 role 搜索此文档。现在当我使用下面的代码时，我得到了两个。我只想获得匹配 user_name 和 role 的数组项。
$where = array (
'_id' => new MongoId ($account_id),
'members.user_id' => new MongoId ($user_id),
'members.role' => $role
);
$this -> cimongo -> where ($where) -> count_all_results ('accounts');
回答by JohnnyHK
This is an old question, but as of MongoDB 2.2 or so you can use the $positional operatorin a projection so that only the matched array element is included in the result.
这是一个老问题，但从 MongoDB 2.2 开始，您可以在投影中使用$位置运算符，以便结果中只包含匹配的数组元素。
So you can do something like this:
所以你可以做这样的事情：
$this->cimongo->where($where)->select(array('members.$'))->get('accounts');
回答by Spencer
This is a repeat of this question:
这是这个问题的重复：
Get particular element from mongoDB array
Also you might want to use $elemMatch
你也可能想使用 $elemMatch
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-ValueinanArray
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-ValueinanArray
Here is the rub -- you aren't going to be able to get the array items that match because mongo is going to return the entire document if those elements match. You will have to parse out the code client side. Mongo doesn't have a way to answer, "return only the array that matches."
这就是问题所在——您将无法获得匹配的数组项，因为如果这些元素匹配，mongo 将返回整个文档。您将不得不解析代码客户端。Mongo 没有办法回答，“只返回匹配的数组”。
