I'm trying to update a nested array in a document only if the array does not already include the item like so:

await userCollection.findOneAndUpdate(
    { _id: ObjectId('616acc597ebda90ca6ffee21') },
    {
      'devices': {
        $push: {
          $cond: {
            if: {
              $in: [req.body.serial, '$devices']
            },
            then: '$devices',
            else: { serial: req.body.serial, data: [] }
          }
        }
      }
    },
    { returnOriginal: false },
    (err, _) => {
      if (err) {
        return res.status(400);
      } else {
        return res.status(200).json(user.value);
      }
    }
  );

This is my user object:

{
    "_id": "616acc597ebda90ca6ffee21",
    "username": "[email protected]",
    "displayName": "Test",
    "devices": [
      {
        "serial": "865674036421275",
        "data": [
          {
            "timestamp": "2021-10-16T12:36:35.799Z"
          },
          {            
            "timestamp": "2021-10-16T12:41:33.633Z"
          },
          {           
            "timestamp": "2021-10-16T12:52:03.055Z"
          }
        ]
      },
      
    ],
    "hashedPassword": "R5vt3vY7vEvTHvhC7YGNOWuIjBUQGLqsd92QGE06tjU=",
    "salt": "6RS0OVIFboCkIEPHdZmTcQ==",
    "dateCreated": "2021-10-16T12:58:00.294Z"
  }

How will I check if serial is already in devices? Also, is it possible to throw an error if it already exists?

CodePudding user response：

There's an update operator called addToSet check it here

CodePudding user response：

Query

• find to update only documents that dont have this serial
• replace the "000" with the serial you want to add
• push in the end
• updateOne will return the result, and you can see if update is done or not, see your driver method details.

*it will be fast, and you dont need an index on devices.serial because it selects a specific document already with the _id match

Test code here

db.collection.update({
  "_id": ObjectId("616acc597ebda90ca6ffee21"),
  "devices.serial": {
    "$ne": "000"
  }
},
{
  "$push": {
    "devices": {
      "serial": "000",
      "data": []
    }
  }
})

We cant mix update operators with aggregate operators. $cond is aggregate operator, it cant be mixed with $push update operator. (aggregate $push is for group, cant add to an array)

We can do the update with update pipeline, but here a normal update is simpler.