$ projection in mongoDB findOneAndUpdate() - node.js

Question

I'm trying to build a simple task queue with express and mongoose. The idea is acquire a single client and return campaign id and client id (which is a subdocument of campaign). Each time someone acquires a client, its status code is set to 1. I've come up with the following query:
router.post('/lease', (err, res) => {
Campaign.findOneAndUpdate({'isEnabled': true, 'clients.contact_status_code': 0}, {
'$set': { 'clients.$.contact_status_code': 1 },
},
{
new: true,
projection: {
'clients.$': true,
},
},
(err, campaign) => {
if (err) {
return res.send(err);
}
res.json(campaign);
}
);
});
But all i'm getting after connecting to this endpoint is this:
{"_id":"591483241a84946a79626aef","clients":[{},{}]}
It seems to me that the problem is with the $ projection, but I have no idea how to fix this.
EDIT: I tried using the following code, utilizing $elemMatch:
router.post('/lease', (err, res) => {
Campaign.findOneAndUpdate({'isEnabled': true, 'clients.contact_status_code': 0}, {
'$set': { 'clients.$.contact_status_code': 1 },
},
{
new: true,
projection: {
clients: {
'$elemMatch': {contact_status_code: 1},
}
},
},
(err, campaign) => {
if (err) {
return res.send(err);
}
res.json(campaign);
}
);
});
Unfortunately, each request yields the first subdocument in the collection, that matched the criteria -- not specifically the one that was updated. Here is an example:
Say, i have the following document in mongo:
{
"_id" : ObjectId("591493d95d48e2738b0d4317"),
"name" : "asd",
"template" : "{{displayname}}",
"isEnabled" : true,
"clients" : [
{
"displayname" : "test",
"_id" : ObjectId("591493d95d48e2738b0d4319"),
"contact_status_code" : 0
},
{
"displayname" : "client",
"_id" : ObjectId("591493d95d48e2738b0d4318"),
"contact_status_code" : 0
}
],
"__v" : 0
}
I run the query for the first time and get the following result:
{"_id":"591493d95d48e2738b0d4317","clients":[{"displayname":"test","_id":"591493d95d48e2738b0d4319","contact_status_code":1}]}
Notice client id "591493d95d48e2738b0d4319" -- this time it runs as expected. But when i run the same query the second time, I get absolutely the same object, although I expect to get one with id "591493d95d48e2738b0d4318".

Answer 1

The issue was with new: true
Here is a working example:
Campaign.findOneAndUpdate({'isEnabled': true, 'clients.contact_status_code': 0}, {
'$set': { 'clients.$.contact_status_code': 1 },
},
{
//new: true <-- this was causing the trouble
projection: {
clients: {
'$elemMatch': {contact_status_code: 0}, // 0 because the old record gets matched
},
},
},
(err, campaign) => {
if (err) {
return res.send(err);
}
res.json(campaign);
}
);
I assume, when the new:true is set, mongo loses the matching context. This approach returns the old record, unfortunately, but that still serves my needs to get the _id.

Answer 2

Seems to me you are getting the campaign id, but you also want clients.$, have you tried clients.$._id?

Answer 3

Update for node MongoDB 3.6 driver
unlike findAndModify the function findOneAndUpdate doesn't have the option new in its options list
But you can use instead returnDocument
returnDocument accept before OR after
When set to after,returns the updated document rather than the original
When set to before,returns the original document rather than the updated.
The default is before.
returnOriginal is Deprecated Use returnDocument instead
Here is a working example:
const filter={'isEnabled': true, 'clients.contact_status_code': 0}
const update={'$set': { 'clients.$.contact_status_code': 1 }}
const options={
returnDocument: 'after' //returns the updated document
projection: {
clients: {
'$elemMatch': {contact_status_code: 0},
// 0 because the old record gets matched
},
},
}
Campaign.findOneAndUpdate(filter,update, options
,(err, campaign) => {
if (err) {
return res.send(err);
}
res.json(campaign);
}
);
findOneAndUpdate Node.js MongoDB Driver API 3.6 documentation