Mongodb 联接不返回具有ObjectId和非ObjectId的结果

我有expertKstag件藏品

{
    _id: ObjectId('6244213ec4c8aa000104d5ba'),
    userID: '60a65e6142e3320001cc8178',
    uid: 'klavidal',
    firstName: 'Kevin',
    name: 'Lavidal',
    email: 'kevin.lavidal@xxx.fr',
    expertProfileInProgressList: {},
    expertProfileList: [
        {
            _id: ObjectId('6453abc94e5cd20001596e1c'),
            version: 0,
            language: 'fr',
            isReference: true,
            state: 'PUBLISHED',
            personalDetails: {
            firstName: 'Kevin',
            name: 'Lavidal',
            email: 'kevin.lavidal@xxx.fr',
                isAbesIDFromLdap: false,
                requiredFieldsLeft: false
            },
            professionalStatus: {
                corpsID: '62442223b8fb982305a5bd67',
                lastUpdateDate: ISODate('2023-05-05T08:36:51.327Z')
            }
    ],
    _class: 'fr.ubordeaux.thehub.expertprofilesservice.model.dao.indexed.ExpertIndexed'
}

和集合nomenclatureKstag

{
    _id: ObjectId('62442223b8fb982305a5bd67'),
    type: 'STATUT_CORPS',
    level: 1,
    hasCNU: true,
    labels: [
        {
            language: 'fr',
            text: 'Enseignant-chercheur'
        },
        {
            language: 'en',
            text: 'Teacher-Researcher'
        }
    ],
    isValid: true
}

我想加入expertKstag-&>expertProfileList.professionalStatus.corpsID和nomenclatureKstag-->_id

我试过了，但什么也没有退回，为什么？

db.expertKstag.aggregate([
   {
      $lookup:
         {
           from: "nomenclatureKstag",
           localField: "expertKstag.expertProfileList.professionalStatus.corpsID",
           foreignField: "_id",
           as: "joinresultat"
         }
   },
   {
      $unwind: "$join_resultat"
   },
   {
      $project: {
         "_id": 1,
         "userID": 1,
         "uid": 1,
         "firstName": 1,
         "name": 1,
         "email": 1,
         "join_resultat.isValid": 1
      }
   }
])

谢谢你的帮助，我认为问题是JOIN _id是ObjectId类型，而expertKstag.expertProfileList.professionalStatus.corpsID不是.