I have two simple models defined in Mongoose, composed of two schema Client and City, I have the property city defined in Client as a ObjectId, ref: 'City', so far so good.
If I query for a client and want also to filter by the 'province' property of City, I do this:
const client = await Client
.find({ name: "Gérard" })
.populate([{
path: 'city',
model: City,
match: { province: 'BA' }
}]);
And the output is just fine:
{
"id": "627264e3ec261a883d42ead9",
"name": "Gérard",
"email": "gerard@depardieu.fr",
"date": "1948-12-27",
"active": true,
"city": {
"id": "627264e3ec261a883d42ead1",
"name": "Buenos Aires",
"province": "BA"
}
}
Howerver, if I input a province code of a nonexistent city:
const client = await Client
.find({ name: "Gérard" })
.populate([{
path: 'city',
model: City,
match: { province: 'CA' }
}]);
It would return me that:
{
"id": "627264e3ec261a883d42ead9",
"name": "Gérard",
"email": "gerard@depardieu.fr",
"date": "1948-12-27",
"active": true,
"city": null
}
I don't want in this particular scenario, any instance of Client to be returned, and I don't know how to avoid this behavior with Mongoose, a behavior I never had to worry about with Spring Data for instance.
Any tips for me?
Thanks in advance.
I solved it myself, I had to go a little lower level with Mongoose and use aggregates and lookups.
const client = await Client.aggregate([
{
$match: { name: "Gérard" }
},
{
$lookup: {
from: City.collection.name,
pipeline: [
{
$match: {
province: 'BA'
}
}
], as: "city"
}
},
{
$unwind: "$city"
},
{
$match: {
city: { $ne: [] }
}
}
]);
Expected result:
{
"id": "627264e3ec261a883d42ead9",
"name": "Gérard",
"email": "gerard@depardieu.fr",
"date": "1948-12-27",
"active": true,
"city": {
"id": "627264e3ec261a883d42ead1",
"name": "Buenos Aires",
"province": "BA"
}
}
Witch is ok, client name "Gérard" lives in "Buenos Aires", situated in province "BA".
On the other hand:
const client = await Client.aggregate([
{
$match: { name: "Gérard" }
},
{
$lookup: {
from: City.collection.name,
pipeline: [
{
$match: {
province: 'CA'
}
}
], as: "city"
}
},
{
$unwind: "$city"
},
{
$match: {
city: { $ne: [] }
}
}
]);
Returns nothing, once the city of "Buenos Aires" is not located in province "CA".
Notice here the last parameter (as an object) the array passed to Client.aggregate() receives:
{
$match: {
city: { $ne: [] }
}
}
This tells MongoDB that in order to return data city must be not equal to an empty array.
And with that the issue is solved.