Mongoose aggregate Lookup - How to filter by specific id

Question

I am trying to make a aggregate pipeline - $lookup to receive from another collection only items that are not equal to specific _id

for example :

Answer 1

You can use below aggregation with mongodb 3.6 and above

You need to just use $match with the child collection as you do with the parent collection in the first stage.

db.BusinessCollection.aggregate([
  { "$match": { "clinics": { "$type": "array" }}},
  { "$lookup": {
    "from": "ClinicsCollection",
    "let": { "clinics": "$clinics" },
    "pipeline": [
      { "$match": {
        "$expr": {
          "$and": [
            { "$in": ["$_id", "$$clinics"] },
            { "$not": { "$eq": ["$_id", 1] }}
          ]
        }
      }}
    ],
    "as": "clinics"
  }}
])