mongo查询-属性是否存在? [英] mongo query - does property exist?

问题描述

在收集文档中，有一个子"属性，该属性是包含1个或多个属性的对象.该集合看起来像:(我已经删除了其他多余的属性)

Within a collection document there is a 'sub' property that is an object containing 1 or more properties. The collection looks like: (I've removes extraneous other properties)

"properties": {
    "source": {
        "a/name": 12837,
        "a/different/name": 76129
    }
}

我需要在集合中进行查找，其中a/name和a/different/name是变量.

I need to do a find on the collection where a/name and a/different/name are variables.

如果您想知道的话，这些变量带有斜杠，因为它们是mqtt主题名称.

The variables have embedded front slashes because they are mqtt topic names, in case you wonder.

(node.js)

我尝试过:

collection.find({'properties.source[variable containing name]': {$exists: true}}).toArray(function...

不起作用，什么也没返回

Doesn't work, nothing returned

我也尝试过设置查询字符串，如下所示:

I've also tried setting a query string as in:

var q = util.format('properties.source.%s', variable containing name);
collection.find({q: {$exists: true}}).toArray(function...

失败，出现查询错误

如果有问题，我可以用其他字符替换前斜杠，但我怀疑它们还可以.我已经尝试过转义前斜杠，但这没什么区别.

I could replace the front slashes with some other character if they are the problem but I suspect they are ok. I have tried escaping the front slashes and it makes no difference.

有什么建议吗?

推荐答案

您不能直接将变量用作对象键，因此需要将其更改为以下内容:

You can't directly use a variable as an object key, so you need to change it to something like:

var name = 'a/name';
var query = {};
query['properties.source.' + name] = {$exists: true};
collection.find(query).toArray(function...

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