How to guarantee unique primary key with one update query - mongodb

Question

In my Movie schema, I have a field "release_date" who can contain nested subdocuments.
These subdocuments contains three fields :
country_code
date
details
I need to guarantee the first two fields are unique (primary key).
I first tried to set a unique index. But I finally realized that MongoDB does not support unique indexes on subdocuments.
Index is created, but validation does not trigger, and I can still add duplicates.
Then, I tried to modify my update function to prevent duplicates, as explained in this article (see Workarounds) : http://joegornick.com/2012/10/25/mongodb-unique-indexes-on-single-embedded-documents/
$ne works well but in my case, I have a combination of two fields, and it's a way more complicated...
$addToSet is nice, but not exactly what I am searching for, because "details" field can be not unique.
I also tried plugin like mongoose-unique-validator, but it does not work with subdocuments ...
I finally ended up with two queries. One for searching existing subdocument, another to add a subdocument if the previous query returns no document.
insertReleaseDate: async(root, args) => {
const { movieId, fields } = args
// Searching for an existing primary key
const document = await Movie.find(
{
_id: movieId,
release_date: {
$elemMatch: {
country_code: fields.country_code,
date: fields.date
}
}
}
)
if (document.length > 0) {
throw new Error('Duplicate error')
}
// Updating the document
const response = await Movie.updateOne(
{ _id: movieId },
{ $push: { release_date: fields } }
)
return response
}
This code works fine, but I would have preferred to use only one query.
Any idea ? I don't understand why it's so complicated as it should be a common usage.

Answer 1

Thanks RichieK for your answer ! It's working great.
Just take care to put the field name before "$not" like this :
insertReleaseDate: async(root, args) => {
const { movieId, fields } = args
const response = await Movie.updateOne(
{
_id: movieId,
release_date: {
$not: {
$elemMatch: {
country_code: fields.country_code,
date: fields.date
}
}
}
},
{ $push: { release_date: fields } }
)
return formatResponse(response, movieId)
}
Thanks a lot !