MongoDB conditionial update - mongodb

Question

I am running a bit in circles here and would appreciate some help. What I am looking to do is either update or create a nested object contained in an array depending on whether this object exists.
I have a users collection and a user document has the following structure:
{
schema_version: 1,
display_name: 'xxxxxx',
email: 'xxxxxx',
email_verified:'xxxxxx',
...
custom_data: {
stripe_id: 'xxx',
subscriptions: [{
subscription_id: xxxx,
....
}],
...
},
}
In webhook calls from Stripe I am getting a subscription object with a subscription_id and a stripe_id.
What I want to do is check if subscription_id exists, if so, update the document, if not then create the document in the subscriptions array for the user document where stripe_id matches.
If I do something along the lines of:
db.collection.update(
{subscription_id: subscription.id},
{ $set: { 'custom_data.subscriptions': subscriptionData } },
{ upsert: true }
)
The problem is that I am creating subscription objects not bound to my user document where stripeID matches.
On the other hand, if I do something like this:
db.collection.update(
{'custom_data.stripe_id': stripe_id},
{ $set: { 'custom_data.subscriptions': subscriptionData } },
{ upsert: true }
)
I will potentially end up creating dupes in the subscriptions array when, in fact I would want to update the existing object where subscription_id matches.
Is there any way to do that in one query with Mongo, or will I have to resort to using 2 queries in an if statement?
Thanks in advance for any clarification on this.

Answer 1

You can do the followings with an aggregation pipeline:
$match with $or condition to search for custom_data.subscriptions.subscription_id or custom_data.stripe_id
$addFields with $map to conditional update your subscription object when matched
$addFields with $setUnion to insert an entry of incoming subscription object for the insert case
$merge to update the back into the original collection
db.collection.aggregate([
{
$match: {
$expr: {
$or: [
{
$eq: [
"$custom_data.subscriptions.subscription_id",
"xxxx"
]
},
{
$eq: [
"$custom_data.stripe_id",
"xxx"
]
}
]
}
}
},
{
"$addFields": {
"custom_data": {
subscriptions: {
"$map": {
"input": "$custom_data.subscriptions",
"as": "s",
"in": {
"$cond": {
// if subscription_id matched, replace with your incoming object
"if": {
$eq: [
"$$s.subscription_id",
"xxxx"
]
},
"then": {
subscription_id: "incoming_sub_id"
},
// if not matched, keep the original object
"else": "$$s"
}
}
}
}
}
}
},
{
"$addFields": {
"custom_data": {
subscriptions: {
// insert case; if the subscription array is empty, then union with your incoming object
$setUnion: [
"$custom_data.subscriptions",
[
{
subscription_id: "incoming_sub_id"
}
]
]
}
}
}
},
{
"$merge": {
"into": "collection",
"on": "_id",
"whenMatched": "replace"
}
}
])
Here is the Mongo playground for your reference.