如何获取mongodb中具有对象ID的所有记录

Question

In the mongodb there is a user data has been stored in collection challange the data seems like bellow:

{
"_id" : 1,
 "name" : "puneet",
 "last" : "jindal",
 "email" : "[e-mail]"
}
{
 "_id" : ObjectId("5b3af82cdb3aaa47792b5fd3"),
 "name" : "hardeep",
 "last" : "singh",
 "email" : "[e-mail]"
}
{ 
 "_id" : 3,
 "name" : "gaurav",
 "last" : "bansal",
 "email" : "[e-mail]"
}
{
 "_id" : ObjectId("5b3af87ddb3aaa47792b5fd4"),
 "name" : "manish",
 "last" : "jindal",
 "email" : "[e-mail]"
}

In the above data there are four records and two of them having id in the integer form and other will having id in object form. I just want to retrieve the all the records which are having the object id in the id field. can anyone tell what query should I write in the code that will only retrieve that records which are having the object id.

Updated:

code I'm using :

type User struct {
 Id              bson.ObjectId    `json:"_id" bson:"_id,omitempty"`
 Name            string    `json:"name,omitempty" bson:"name,omitempty"`
 Last            string `json:"last,omitempty" bson:"last,omitempty"`
 Email          string `json:"email,omitempty" bson:"email,omitempty"`
}
type Users []User

func GetAllUsers(listQuery interface{}) (result Users, err error) {
 mongoSession := config.ConnectDb()
 sessionCopy := mongoSession.Copy()
 defer sessionCopy.Close()
 getCollection := mongoSession.DB(config.Database).C(config.UsersCollection)
 err = getCollection.Find(listQuery).Select(bson.M{"password": 0}).All(&result)
 if err != nil {
    return result, err
 }
 return result, nil
}

conditions := bson.M{'_id': bson.M{'$type': "objectId" } }
data, err := models.GetAllUsers(conditions) 

The error I'm facing by using this :-

controllers/UserController.go:18:23: invalid character literal (more than one character) controllers/UserController.go:18:28: cannot use '\u0000' (type rune) as type string in map key

Answer 1

'_id' and '$type' are invalid rune literals, you can't list multiple runes (characters) in a rune literal (only a single rune).

The bson.M type is a map with string key type, so you have to use string literals (or expressions), like this:

conditions := bson.M{"_id": bson.M{"$type": "objectId"}}

Also note that the bson package holds constants for the different types, so it's safer to use those constants:

conditions := bson.M{"_id": bson.M{"$type": bson.ElementObjectId}}