$filter upto 2 nested level in mongodb

Answer 1

You need to $unwind the first array then you can easily apply $filter on the nested array

db.collection.aggregate([
  { "$unwind": "$Hospitais" },
  { "$match": { "Hospitais.nome": "Dorio Silva" } },
  { "$project": {
    "Hospitais": {
      "$filter": {
        "input": "$Hospitais.utis",
        "as": "uti",
        "cond": {
          "$eq": ["$$uti.nome", "UTI1"]
        }
      }
    }
  }}
])

Or you can try this as well

db.collection.aggregate([
  { "$match": { "Hospitais.nome": "Dorio Silva" } },
  { "$project": {
    "Hospitais": {
      "$filter": {
        "input": {
          "$map": {
            "input": "$Hospitais",
            "as": "hospital",
            "in": {
              "nome": "$$hospital.nome",
              "utis": {
                "$filter": {
                  "input": "$$hospital.utis",
                  "as": "uti",
                  "cond": {
                    "$eq": ["$$uti.nome", "UTI1"]
                  }
                }
              }
            }
          }
        },
        "as": "hospital",
        "cond": {
          "$eq": ["$$hospital.nome", "Dorio Silva"]
        }
      }
    }
  }}
])

Both will give the similar output

[
  {
    "Hospitais": [
      {
        "_id": 893910,
        "leitos": [
          {
            "_id": 1.2893812e+08,
            "_paciente": "Oliver"
          },
          {
            "_id": 1.2803918239e+10,
            "_paciente": "Priscilla"
          }
        ],
        "nome": "UTI1"
      }
    ]
  }
]