具有Mongoose限制子文档的MongoDB [英] MongoDB with Mongoose limit subdocuments

问题描述

在MongoDB和Mongoose方面，我是个菜鸟，请原谅我...

I am a noob when it comes to MongoDB and Mongoose so please forgive me...

我正在将Node与Express和Mongoose一起使用.我有一个包含大量子文档的文档，以至于当我尝试加载所有子文档时，我的服务器内存不足.因此，我想选择一个子文档的最后30个项目.这是我现在所拥有的，然后是我想我想要的东西的猜测...

I am using Node with Express along with Mongoose. I have a document with a ton of subdocuments, so much so that my server runs out of memory when trying to load all the subdocuments. So I want to select the last 30 items of a subdocument. Here is what I have now, and then a guess as to what I think I want...

Device.findOne({ device_id: deviceId }, (err, device) => {
        ....
})

这是个猜测

Device.findOne({ device_id: deviceId }, { movements: { $slice: 30 } }, (err, device) => {
        ....
})

任何帮助都会很棒，在此先谢谢您！

Any help would be awesome, thanks in advance!!!

推荐答案

您几乎钉牢了它.

要获取最后30个值，只需使用减号即可.就您而言，您可以执行以下操作:

To get the last 30 values, just use minus instead. In your case, you can do something like:

Device.findOne({ device_id: deviceId }, { movements: { $slice: -30 } }, (err, device) => {
        ....
})

希望有帮助.

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