how to update property in nested mongo document - mongodb

Question

I want to update a particular property in a nested mongo document
{
"_id" : ObjectId("55af76e60b0e4b318ba822ec"),
"make" : "MERCEDES-BENZ",
"model" : "E-CLASS",
"variant" : "E 250 CDI CLASSIC",
"fuel" : "Diesel",
"cc" : 2143,
"seatingCapacity" : 5,
"variant_+_fuel" : "E 250 CDI CLASSIC (Diesel)",
"make_+_model_+_variant_+_fuel" : "MERCEDES-BENZ E-CLASS E 250 CDI CLASSIC (Diesel)",
"dropdown_display" : "E-CLASS E 250 CDI CLASSIC (Diesel)",
"vehicleSegment" : "HIGH END CARS",
"abc" : {
"variantId" : 1000815,
"makeId" : 1000016,
"modelId" : 1000556,
"fuelId" : 2,
"segmentId" : 1000002,
"price" : 4020000
},
"def" : {
"bodyType" : 1,
"makeId" : 87,
"modelId" : 21584,
"fuel" : "DIESEL",
"vehicleSegmentType" : "E2"
},
"isActive" : false
}
This is my document. If I want to add or update a value for key "nonPreferred" inside "abc", how do I go about it?
I tried it with this query:
db.FourWheelerMaster.update(
{ "abc.modelId": 1000556 },
{
$Set: {
"abc": {
"nonPreferred": ["Mumbai", "Pune"]
}
}
},
{multi:true}
)
but it updates the whole "abc" structure, removed all key:values inside it and kept only newly inserted key values like below
"abc" : {
"nonPreferred" : [
"Mumbai",
"Pune"
]
},
Can anyone tell me how to update only particular property inside it and not all the complete key?

Answer 1

Instead of using the $set operator, you need to push that array using the $push operator together with the $each modifier to append each element of the value separately as follows:
db.FourWheelerMaster.update(
{ "abc.modelId": 1000556 },
{
"$push": {
"abc.nonPreferred": {
"$each": ["Mumbai", "Pune"]
}
}
},
{ "multi": true }
)