如何在mongo/node/mongoose中获得值数组而不是json数组?

I'm trying to simulate a join in a mongo query so I'm taking the results of my 1st query and then passing it as a $in filter to my 2nd query.

我试图模拟mongo查询中的一个连接，所以我取第一个查询的结果，然后将它作为$in过滤器传递给第二个查询。

Unfortunately the results of my 1st query returns an array of json objects like so

不幸的是，第一个查询的结果返回一个json对象数组

[ { _id: 4ecd830da046050100000025 },
  { _id: 4ecd84a0a046050100000085 } ]

and the $in filter doesn't return anything because they are json objects instead of a value array. I can manually transform that array but is there a built in method or function that I can use? Also, is there a way I can have mongo return the value array instead? Currently I am calling the find query as such

$in过滤器不会返回任何东西，因为它们是json对象而不是值数组。我可以手动转换那个数组，但是有内置的方法或函数可以使用吗?另外，是否有办法让mongo返回值数组?目前我正在调用find查询

Likes.find {liker:"Me"}, {_id:1}, {safe:true}

And here is my 2nd query

这是我的第二个问题

Post.find {_id:{$in:likes}}

I was hoping for something like

我希望能有这样的机会。

Post.find {_id:{$in:likes._id}}

1 个解决方案

#1

Although there is no general solution to your question in the case of $in clauses you can use the result of a distinct operation :

虽然你的问题在$in条款中没有通用的解决方案，但你可以使用不同操作的结果:

> db.test.save({a:1})
> db.test.save({a:2})
> db.test.save({a:3})
> db.test.save({a:4})

> ids = db.test.distinct("_id", {a:{$gt:2}})
[
        ObjectId("4ece45c2c951f11718678574"),
        ObjectId("4ece45c4c951f11718678575")
]

> db.test.find({_id:{$in:ids}})
{ "_id" : ObjectId("4ece45c2c951f11718678574"), "a" : 3 }
{ "_id" : ObjectId("4ece45c4c951f11718678575"), "a" : 4 }

Hope that helps!

希望会有帮助!

#1