Pulling from a value from a collection in Mongo

Question

How do I pull a value from a collection in Mongo?

This is the query I'ved tried used to pull one of the values in one of the collections.

I am trying to delete a value in the array in the collection srs.5689f5206f404774fc350407

db.dbName.update(
{ _id: ObjectId("5689e240d3235cbef83e41d0") },
{ $pull:{ 'srs.5689f5206f404774fc350407.$.flashcardID':
          ObjectId("5689f52e6f404774fc35040a")}
})

This is the document in question.

{
   "_id":ObjectId("5689e240d3235cbef83e41d0"),
   "username":"lol1",
   "score":"",
   "decks":[
      "5689e246d3235cbef83e41d1"
   ],
   "srs":{
      "5689e246d3235cbef83e41d1":[
         {
            "timer":1451876940132,
            "flashcardID":ObjectId("5689e24cd3235cbef83e41d2"),
            "correct":0,
            "type":"srs"
         },
         {
            "timer":1451876944421,
            "flashcardID":ObjectId("5689e250d3235cbef83e41d3"),
            "correct":0,
            "type":"srs"
         },
         {
            "timer":1451876949586,
            "flashcardID":ObjectId("5689e255d3235cbef83e41d4"),
            "correct":0,
            "type":"srs"
         },
         {
            "timer":1451876954478,
            "flashcardID":ObjectId("5689e25ad3235cbef83e41d5"),
            "correct":0,
            "type":"srs"
         },
         {
            "timer":1451876957760,
            "flashcardID":ObjectId("5689e25dd3235cbef83e41d6"),
            "correct":0,
            "type":"srs"
         }
      ]
   },
   "type":"user"
}

WriteResult({
        "nMatched" : 0,
        "nUpserted" : 0,
        "nModified" : 0,
        "writeError" : {
                "code" : 16837,
                "errmsg" : "The positional operator did not find the match needed from the query. Unexpanded update: srs.5689f5206f404774fc350407.$.flashcardID"
        }
})

I would like some advice on what to do. I've tried fixing this query for quite awhile.

Answer 1

db.dbName.update({
        _id: "5689e240d3235cbef83e41d0"
}, {
    $pull: {
        "srs.5689e246d3235cbef83e41d1": {
            "flashcardID": "5689e24cd3235cbef83e41d2"
        }
    }
})

Try this. You need to tell what you want to pull that is the first key after "$pull" in this case "srs.5689e246d3235cbef83e41d1" then the where clause to find your value ""flashcardID": "5689e24cd3235cbef83e41d2"". Read the documentation https://docs.mongodb.org/manual/reference/operator/update/pull/

Answer 2

1. It appears the schema is not using an objectid -- but a string. unless pretty printed...

2. $ is not a operator. you may be thinking of the $in operator. in this case it seems it is not needed just use the flashcard string.

   db.dbName.update( { _id: "5689e240d3235cbef83e41d0" }, { $pull: {"srs.5689f5206f404774fc350407": {"flashcardID": "5689f52e6f404774fc35040a"}}} )