I was wondering, is there a way in MongoDB to get all the documents from one collection excluding those that exists in another, without using aggregation.
Let me explain myself more;
I have a collection of "Users", and another collection where there is an array of objects. Something like this:
User
}
"_id": "61e6bbe49d7efc57f895ab50",
"name": "User 1"
},
{
"_id": "61e6b9239d7efc57f895ab02",
"name": "User 2"
},
{
"_id": "61cae6176d0d9a36efd8f190",
"name": "User 3"
},
{
"_id": "61cade886d0d9a36efd8f11a",
"name": "User 4"
},
The other collection looks like this:
{
users: [
{
user: {
"_id": "61e6b9239d7efc57f895ab02",
"name": "User 2",
},
...
},
{
user: {
"_id": "61cae6176d0d9a36efd8f190",
"name": "User 3",
},
...
},
],
},
I would like to get all the users in "array 1" excluding those in "array 2". So the result should be:
[
{
"_id": "61e6b9239d7efc57f895ab02",
"name": "User 1"
},
{
"_id": "61cae6176d0d9a36efd8f190",
"name": "User 4"
},
],
So, is there a way to do that without the need to do aggregation.
you can use the $and like this:
const found = await User.find({
$and: [
{ _id: { $in: array1 } },
{ _id: { $nin: array2 } }
]
});
For anyone looking for a solution, if you want to add new element to an array of objects, where you, somehow, forgot to initialize the _id field, remember you have to, because mongo adds that field automatically (to use it for filtering/indexation).
All you have to do, is to write something like this;
const data = Data.create({
_id: mongoose.Types.ObjectId.createFromHexString(uid),
users: [{ user: userId, initiator: true, _id: userId}],
})
and for the searching, you write what you always write;
const found = await User.find({ _id: { $nin: data.users } });