通过mongoDB中的键在列表内获取字典(mongoengine) [英] Getting a dictionary inside a list by key in mongoDB (mongoengine)

问题描述

我在Flask应用程序(mongoengine)中使用mongoDB(mongoHQ). 我有一个Document看起来像这样:

I'm using mongoDB (mongoHQ) in my Flask app (mongoengine). I have a Document that looks like this:

{items: [{id: 1}, {id: 2}, {id: 3}]}

例如，在单个查询中是否可以通过id: 1到达dict?

Is there a way to to reach, for example, the dict with id: 1 in a single query?

目前，我正在使用next()语句遍历items列表，并且希望有一个更明智的解决方案.谢谢

Currently I'm looping through the items list with a next() statement and I was hoping for a wiser solution. Thanks

推荐答案

我对MongoEngine不熟悉，但是$ projection运算符可以过滤数组以仅显示匹配的元素.在Mongo Shell中:

I'm not familiar with MongoEngine, but the $ projection operator can filter an array to show only the matched element. In the Mongo shell:

> db.foo.insert({"items": [{"id": 1}, {"id": 2}, {"id": 3}]})
> db.foo.find({'items.id': 1}, {'items.$': true})
{ "_id" : ObjectId("51ce29b68b178484ff2a01ed"), "items" : [  {  "id" : 1 } ] }

更多信息: http://docs.mongodb.org/manual/reference/投影/位置/

您似乎在MongoEngine中做到了:

It seems in MongoEngine you do:

Foo.objects(__raw__={'items.id': 1}).only('items.$')

更多: http://mongoengine-odm. readthedocs.org/en/latest/guide/querying.html#raw-queries

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