In the collection, I have entries as such:
[
{
_id: new ObjectId('61cae11f8fc0b2e3b045be04'),
location: 'Station One',
datetime: ISODate('2019-02-02T12:54:57.937Z'),
sensorType: 'temperature',
value: -1.8,
__v: 0,
},
{
_id: new ObjectId('61cae11f8fc0b2e3b045be05'),
location: 'Station two',
datetime: ISODate('2019-02-02T09:49:39.200Z'),
sensorType: 'temperature',
value: -2,
__v: 0,
},
];
I have a aggregate query to get min/max values of each sensortype like so
const queryMinMax = FarmDataModel.aggregate([
{
$match: match,
},
{
$sort: {
value: 1,
},
},
{
$group: {
_id: {
sensorType: '$sensorType', location: '$location',
},
min: {
$first: '$$ROOT',
},
max: {
$last: '$$ROOT',
},
},
},
{
$sort: {
'_id.location': 1,
'_id.sensorType': 1,
},
},
{
$project: {
_id: 1,
max: {
value: '$max.value',
month: { $month: '$max.datetime' },
year: { $year: '$max.datetime' },
day: { $dayOfMonth: '$max.datetime' },
},
min: {
value: '$min.value',
month: { $month: '$min.datetime' },
year: { $year: '$min.datetime' },
day: { $dayOfMonth: '$min.datetime' },
},
},
},
]);
This gets me a row for each sensortype and corresponding min max values. What Id like to do is group each sensortype under a location, so that query would return something like so:
{
'Station One': {
temperature: {
min: { value: number; date: date }
max: { value: number; date: date },
},
pH: {
min: { value: number; date: date }
max: { value: number; date: date },
},
},
'Station Two': {
temperature: {
min: { value: number; date: date }
max: { value: number; date: date },
},
pH: {
min: { value: number; date: date }
max: { value: number; date: date },
},
},
};
So if before I would get 4 rows, one for each sensorType in each location, now I would get two rows, one for each location and under those there are key:value pairs for each sensorType
Hoe can I modify my query to achieve that?
You can just build on your existing pipeline, all it takes is another $group stage to group the data by station, then some restructuring of it to match the output you want, like so:
db.collection.aggregate([
... existing pipeline,
{
$group: {
_id: "$_id.location",
sensorData: {
$push: {
k: "$_id.sensorType",
v: {
max: "$max",
min: "$min"
}
}
}
}
},
{
"$replaceRoot": {
"newRoot": {
"$arrayToObject": [
[
{
k: "$_id",
v: {
"$arrayToObject": "$sensorData"
}
}
]
]
}
}
}
])