Forming an array with aggregation in MongoDB - mongodb

Question

I have a document in MongoDB 3.4 with the following structure:
{
"_id" : ObjectId("5e3419e468d01013eadb83dc"),
"id_station" : "62",
"fiware_service" : null,
"fiware_servicepath" : null,
"id_fiware_name" : "CE_del_medio",
"attrName" : "15",
"attrType" : "float",
"attrValue" : 0.33,
"id_sensor_station_absolute" : "15_62",
"recvTimeTs" : 1580387045,
"recvTime" : "2020-01-30T12:24:05.00Z",
"id_fiware" : "15",
"sensor_type" : [
{
"name" : "id",
"type" : "String",
"value" : "15"
},
{
"name" : "img",
"type" : "String",
"value" : "assets/img/contrast.png"
},
{
"name" : "manufacturer",
"type" : "String",
"value" : "Hortisis"
},
{
"name" : "medida",
"type" : "String",
"value" : "mS/cm"
},
{
"name" : "name_comun",
"type" : "String",
"value" : "CE del medio"
},
{
"name" : "place",
"type" : "String",
"value" : "interior"
},
{
"name" : "timestamp",
"type" : "DateTime",
"value" : "2020-01-30T12:24:05.00Z"
},
{
"name" : "type",
"type" : "String",
"value" : "fertigation"
}
]
}
I need to convert the sensor_type field to an array with only one object, as follows:
{
"_id":"15_62",
"medidas":[
{
"_id":"5e3419e468d01013eadb83dc",
"marca":"Hortisis",
"modelo":"Estacion",
"fabricante":"Hortisis",
"id_station":"15",
"sensor_type":[
{
"name":"15",
"type":"fertigation",
"place":"interior",
"img":"assets/img/contrast.png",
"name_comun":"Temp. Suelo",
"medida":"mS/cm"
}
],
"attrName":"15",
"attrValue":0.33,
"recvTimeTs":1580387045,
"recvTime":"2020-01-30T12:24:05.00Z",
"id_sensor_station_absolute":"15_62"
}
]
}
As you can really see it is formatting the sensor_type field = name : value.
I'm working with NODEJS and mongoose.
This is my query: (first I search, sort, only show the first value and then with the project I give format, the problem is that I don't know how to tell the project to put that format if I put "sensor_type": "$latest.attributes.name") it only shows the names and I don't know how to put it in the mentioned format.
Datagreenhouse.aggregate([
{ "$match": { "id_sensor_station_absolute": { "$in": array3 } } }, // "id_station": { "$in": id_station },
{ "$sort": { "recvTime": -1 } },
{
"$group": {
"_id": "$id_sensor_station_absolute",
"latest": { "$first": "$$ROOT" },
}
},
{
"$project": {
"_id": 1,
"id_station": "$latest.id_station",
//"id_sensor_station_absolute": "$id_sensor_station_absolute",
"attrName": "$latest.attrName",
"attrValue": "$latest.attrValue",
"recvTimeTs": "$latest.recvTimeTs",
"recvTime": "$latest.recvTime",
"id_sensor_station_absolute": "$latest.id_sensor_station_absolute",
"sensor_type": "$latest.attributes",
"name": { $arrayElemAt: ["$latest.attributes", 0] },
"type": { $arrayElemAt: ["$latest.attributes", 1] },
"place": { $arrayElemAt: ["$latest.attributes", 2] },
"img": { $arrayElemAt: ["$latest.attributes", 1] },
"name_comun": { $arrayElemAt: ["$latest.attributes", 4] },
"medida": { $arrayElemAt: ["$latest.attributes", 3] },
"interfaz": { $arrayElemAt: ["$latest.attributes", 6] },
}
}
], (err, DatagreenhouseRecuperado) => {
if (err) return res.status(500).send({ message: 'Error al realizar la peticion' + err })
if (!DatagreenhouseRecuperado) return res.status(404).send({ message: 'Error el usuario no existe' })
res.status(200).send({ DatagreenhouseRecuperado })
})
Thank you for your help. Best regards.

Answer 1

Since version 3.4.4, MongoDB introduced a magnific operator: $arrayToObject
This operator allows us transmute array key:value pair into object.
Syntax
RAW DATA $map $arrayToObject
sensor_type : [ sensor_type : [ sensor_type : {
{ \ { \
"name" : "manufacturer", ----> k: "manufacturer", --->
"type" : "String", / v: "Hortisis" / "manufacturer" : "Hortisis"
"value" : "Hortisis"
} }
] ] }
db.datagreenhouses.aggregate([
{
"$match": {} // setup your match criteria
},
{
"$sort": {
"recvTime": -1
}
},
{
$group: {
_id: "$id_sensor_station_absolute",
medidas: {
$push: {
_id: "$_id",
"marca": "Hortisis", // don't know where you get this value
"modelo": "Estacion", // don't know where you get this value
"id_station": "$id_station",
"attrName": "$attrName",
"attrValue": "$attrValue",
"recvTimeTs": "$recvTimeTs",
"recvTime": "$recvTime",
"id_sensor_station_absolute": "$id_sensor_station_absolute",
"sensor_type": {
$arrayToObject: {
$map: {
input: "$sensor_type",
in: {
k: "$$this.name",
v: "$$this.value"
}
}
}
}
}
}
}
}
])
MongoPlayground
[
{
"_id": "15_62",
"medidas": [
{
"_id": ObjectId("5e3419e468d01013eadb83dc"),
"attrName": "15",
"attrValue": 0.33,
"id_sensor_station_absolute": "15_62",
"id_station": "62",
"marca": "Hortisis",
"modelo": "Estacion",
"recvTime": "2020-01-30T12:24:05.00Z",
"recvTimeTs": 1.580387045e+09,
"sensor_type": {
"id": "15",
"img": "assets/img/contrast.png",
"manufacturer": "Hortisis",
"medida": "mS/cm",
"name_comun": "CE del medio",
"place": "interior",
"timestamp": "2020-01-30T12:24:05.00Z",
"type": "fertigation"
}
}
]
}
]
All you need to do is transform data to the desired result with an easy to handle object ($unwind medidas field, transform and then $group again)
Note: If your MongoDB is earlier 3.4.4 version, follow update procedure:
Install MongoDB 3.4.4 or newer
Make mongodump with new version MongoBD
Stop old MongoBD
Remove /data directory (make backup)
Start new MongoDB and run mongorestore