MongoDB - Update or Insert object in array

Question

I have the following collection

{
    "_id" : ObjectId("57315ba4846dd82425ca2408"),
    "myarray" : [ 
        {
            use         


        

Answer 1

I haven't found any solutions based on a one atomic query. Instead there are 3 ways based on a sequence of two queries:

1. always $pull (to remove the item from array), then $push (to add the updated item to array)

   db.collection.update(
                  { _id : ObjectId("57315ba4846dd82425ca2408")},
                  { $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
   )
   
   db.collection.update(
                  { _id : ObjectId("57315ba4846dd82425ca2408")},
                  {
                    $push: {
                             "myarray": {
                                         userId:ObjectId("570ca5e48dbe673802c2d035"),
                                         point: 10
                                        }
                            }
                   }
   )
   

2. try to $set (to update the item in array if exists), then get the result and check if the updating operation successed or if a $push needs (to insert the item)

   var result = db.collection.update(
       {
          _id : ObjectId("57315ba4846dd82425ca2408"),
         "myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
       },
       {
          $set: {"myarray.$.point": {point: 10}}
       }
    );
   
   if(!result.nMatched){
          db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
                               {
                                 $addToSet: {
                                              myarray: {
                                                 userId: ObjectId("570ca5e48dbe673802c2d035"),
                                                 point: 10
                                             }
                               }
          );
   

3. always $addToSet (to add the item if not exists), then always $set to update the item in array

      db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
                            myarray: { $not: { $elemMatch: {userId: ObjectId("570ca5e48dbe673802c2d035")} } } },
                           { 
                              $addToSet : {
                                            myarray: {
                                                       userId: ObjectId("570ca5e48dbe673802c2d035"),
                                                       point: 10
                                                      }
                                           }
                            },
                           { multi: false, upsert: false});
   
      db.collection.update({
                             _id: ObjectId("57315ba4846dd82425ca2408"),
                              "myArray.userId": ObjectId("570ca5e48dbe673802c2d035")
                           },
                           { $set : { myArray.$.point: 10 } },
                           { multi: false, upsert: false});
   

1st and 2nd way are unsafe, so transaction must be established to avoid two concurrent requests could push the same item generating a duplicate.

3rd way is safer. the $addToSet adds only if the item doesn't exist, otherwise nothing happens. In case of two concurrent requests, only one of them adds the missing item to the array.