在查找中使用$ slice

Question

I have a mongodb document which contains an array called "data". I want to be able to only get certain ranges from the array.In robo 3T I am able to run db.getCollection('collection').find({"_id": "user1"},{data:{$slice:[1,4]]} ) to get 4 elements from the data array from position 1.

How can I run the same query in golang?

What I tried:

c.Find(bson.M{"_id":"user1" , "data":bson.M{"$slice":[]int{1,4}}}  )

but i get "unknown operator $slice" Not sure what to do. Any help please?

Mongo Doc

{
  "_id": "user1",
  "time": 32467777,

 "data": [

     88,
     45,
     1,
     4,
     7,
     123,
      33,
     132

 ]


}

Answer 1

The second argument you pass to MongoDB's find() is a projection, for which the equivalent in mgo is the Query.Select().

So you may do what you want like this:

var results bson.M
err := c.Find(
    bson.M{"_id": "user1"},
).Select(
    bson.M{"data": bson.M{"$slice": []int{1, 4}}},
).One(&results)

Also note that to query something exclusively by its ID, you may use the Collection.FindId(), so you may write it more compact like this:

var results bson.M
err := c.FindId("user1").Select(
    bson.M{"data": bson.M{"$slice": []int{1, 4}}},
).One(&results)