Update nested subdocuments in MongoDB with arrayFilters

Question

I need to modify a document inside an array that is inside another array. I know MongoDB doesn\'t support multiple \'$\' to iterate on multiple arrays at the same time, but

Answer 1

So the arrayFilters option with positional filtered $[<identifier>] does actually work properly with the development release series since MongoDB 3.5.12 and also in the current release candidates for the MongoDB 3.6 series, where this will actually be officially released. The only problem is of course is that the "drivers" in use have not actually caught up to this yet.

Re-iterating the same content I have already placed on Updating a Nested Array with MongoDB:

NOTE Somewhat ironically, since this is specified in the "options" argument for .update() and like methods, the syntax is generally compatible with all recent release driver versions.

However this is not true of the mongo shell, since the way the method is implemented there ( "ironically for backward compatibility" ) the arrayFilters argument is not recognized and removed by an internal method that parses the options in order to deliver "backward compatibility" with prior MongoDB server versions and a "legacy" .update() API call syntax.

So if you want to use the command in the mongo shell or other "shell based" products ( notably Robo 3T ) you need a latest version from either the development branch or production release as of 3.6 or greater.

All this means is that the current "driver" implementation of .update() actually "removes" the necessary arguments with the definition of arrayFilters. For NodeJS this will be addressed in the 3.x release series of the driver, and of course "mongoose" will then likely take some time after that release to implement it's own dependencies on the updated driver, which would then no longer "strip" such actions.

You can however still run this on a supported server instance, by dropping back to the basic "update command" syntax usage, since this bypassed the implemented driver method:

const mongoose = require('mongoose'),
      Schema = mongoose.Schema,
      ObjectId = mongoose.Types.ObjectId;

mongoose.Promise = global.Promise;
mongoose.set('debug',true);

const uri = 'mongodb://localhost/test',
      options = { useMongoClient: true };

const contactSchema = new Schema({
  data: String,
  type: String,
  priority: String,
  retries: String
});

const personSchema = new Schema({
  name: String,
  level: String,
  priority: String,
  enabled: Boolean,
  contacts: [contactSchema]
});

const groupSchema = new Schema({
  name: String,
  people: [personSchema],
  workingHours: { start: String, end: String },
  workingDays: { type: [Number], default: undefined },
  contactTypes: {
    workingHours: { type: [String], default: undefined },
    contactTypes: { type: [String], default: undefined }
  }
});

const Group = mongoose.model('Group', groupSchema);

function log(data) {
  console.log(JSON.stringify(data, undefined, 2))
}

(async function() {

  try {

    const conn = await mongoose.connect(uri,options);

    // Clean data
    await Promise.all(
      Object.entries(conn.models).map(([k,m]) => m.remove() )
    );

    // Create sample

    await Group.create({
      name: "support",
      people: [
        {
          "_id": ObjectId("5a05a8c3e0ce3444f8ec5bd8"),
          "enabled": true,
          "level": "1",
          "name": "Someone",
          "contacts": [
            {
              "type": "email",
              "data": "adifferent.email@example.com"
            },
            {
              "_id": ObjectId("5a05a8dee0ce3444f8ec5bda"),
              "retries": "1",
              "priority": "1",
              "type": "email",
              "data": "some.email@example.com"
            }
          ]
        }
      ]
    });

    let result = await conn.db.command({
      "update": Group.collection.name,
      "updates": [
        {
          "q": {},
          "u": { "$set": { "people.$[i].contacts.$[j].data": "new data" } },
          "multi": true,
          "arrayFilters": [
            { "i._id": ObjectId("5a05a8c3e0ce3444f8ec5bd8") },
            { "j._id": ObjectId("5a05a8dee0ce3444f8ec5bda") }
          ]
        }
      ]
    });

    log(result);

    let group = await Group.findOne();
    log(group);

  } catch(e) {
    console.error(e);
  } finally {
    mongoose.disconnect();
  }

})()

Since that sends the "command" directly through to the server, we see the expected update does in fact take place:

Mongoose: groups.remove({}, {})
Mongoose: groups.insert({ name: 'support', _id: ObjectId("5a06557fb568aa0ad793c5e4"), people: [ { _id: ObjectId("5a05a8c3e0ce3444f8ec5bd8"), enabled: true, level: '1', name: 'Someone', contacts: [ { type: 'email', data: 'adifferent.email@example.com', _id: ObjectId("5a06557fb568aa0ad793c5e5") }, { _id: ObjectId("5a05a8dee0ce3444f8ec5bda"), retries: '1', priority: '1', type: 'email', data: 'some.email@example.com' } ] } ], __v: 0 })
{ n: 1,
  nModified: 1,
  opTime:
   { ts: Timestamp { _bsontype: 'Timestamp', low_: 3, high_: 1510364543 },
     t: 24 },
  electionId: 7fffffff0000000000000018,
  ok: 1,
  operationTime: Timestamp { _bsontype: 'Timestamp', low_: 3, high_: 1510364543 },
  '$clusterTime':
   { clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 3, high_: 1510364543 },
     signature: { hash: [Object], keyId: 0 } } }
Mongoose: groups.findOne({}, { fields: {} })
{
  "_id": "5a06557fb568aa0ad793c5e4",
  "name": "support",
  "__v": 0,
  "people": [
    {
      "_id": "5a05a8c3e0ce3444f8ec5bd8",
      "enabled": true,
      "level": "1",
      "name": "Someone",
      "contacts": [
        {
          "type": "email",
          "data": "adifferent.email@example.com",
          "_id": "5a06557fb568aa0ad793c5e5"
        },
        {
          "_id": "5a05a8dee0ce3444f8ec5bda",
          "retries": "1",
          "priority": "1",
          "type": "email",
          "data": "new data"            // <-- updated here
        }
      ]
    }
  ]
}

So right "now"^[1] the drivers available "off the shelf" don't actually implement .update() or it's other implementing counterparts in a way that is compatible with actually passing through the necessary arrayFilters argument. So if you are "playing with" a development series or release candiate server, then you really should be prepared to be working with the "bleeding edge" and unreleased drivers as well.

But you can actually do this as demonstrated in any driver, in the correct form where the command being issued is not going to be altered.

^[1] As of writing on November 11th 2017 there is no "official" release of MongoDB or the supported drivers that actually implement this. Production usage should be based on official releases of the server and supported drivers only.