Database
[{
"_id": "1",
"device_id": "ML39A-341D4-UI041",
"date": "2018-03-28T00:00:00.000Z"
},
{
"_id": "2",
"device_id": "ML39A-341D4-UI041",
"date": "2018-03-29T00:00:00.000Z"
},
{
"_id": "3",
"device_id": "D4YK2-R2D20-KYPI9",
"date": "2018-04-01T00:00:00.000Z"
}
]
Query
db.collection.aggregate([{
"$group": {
"_id": "$device_id",
"dt": {
"$push": "$date"
}
}
}, {
"$replaceRoot": {
"newRoot": {
"$arrayToObject": {
"$concatArrays": [
[{
"k": "$_id",
"v": "$dt"
}]
]
}
}
}
}])