delete object from nested document in mongodb - json

Question

I have this JSON above with _id, date, and two objects: sessionData and metaData. I want to delete from every document the object metaData where "userId":123456
{
"_id": {
"$oid": "60feedd4b3aefff2629b93b7"
},
"insertionDate": {
"$date": "2021-07-26T18:15:57.564Z"
},
"sessionData": {
"time": [1364, 1374, 1384],
"yaw": [0.15, 0.3, 0.45],
"pitch": [0.36, 0.76, 1.08],
"roll": [-0.13, -0.25, -0.35],
"heading": [-3.24, -3.25, -3.17],
"ax": [-0.42, -0.41, -0.41],
"ay": [-0.15, -0.13, -0.1],
"az": [0.9, 0.91, 1],
"gx": [0, 0, 0],
"gy": [-0.01, 0, -0.01],
"gz": [0.02, 0.02, 0.02],
"mx": [0.26, 0.26, 0.26],
"my": [0.01, 0.01, 0.01],
"mz": [-0.04, -0.04, -0.07]
},
"metaData": {
"userId": 123456,
"gender": "M",
"ageGroup": "SENIOR",
"weightKg": 70,
"heightCm": 175,
"poolSizeM": 50
}
}
The code I have:
#app.route('/data/anonymousData/<int:l>', methods = ['POST'])
def makeanonymous(l):
result = collection.update_many({}, {"$pull":{ "metaData": {"$in": {"userId": l }}}}, multi=True )
t=result.deleted_count
return f'Deleted {t} documents.'

Answer 1

You can use $unset to remove the object like this:
collection.update_many({
"metaData.userId": 123456
},
{
"$unset": {
"metaData": ""
}
})
Check this example.