My database has data in the following format :
{ "_id" : ObjectId( "abcd" ),
"coordinate" : [somevalue, somevalue],
"value" : [
{ "time" : 1,
"characteristics" : "pqrs" },
{ "time" : 10,
"characteristics" : "pqrs" } ] }
I want to find the field closest coordinate and a time that is less than or equal to a given value.
Currently I'm using this query :
db.collection.aggregate({
coordinate: {
$geoNear: [latitude, longitude],
$maxDistance: 10
},
"value.time": {
$lte: 5
}
})
This one returned the entire entry, but what I wanted is the field:
{ "time" : 1, "characteristics" : "pqrs" }
Is it even possible to just return this field ? What if there are multiple result and I just want the one that's closest to my value.time input ?
You can perform an aggregation to :
$match items with specified coordinate and value.time$filter value array to remove everything < 5$unwind value array$group by max valueQuery is :
db.collection.aggregate({
$match: {
coordinate: {
$geoNear: [0, 0],
$maxDistance: 10
},
"value.time": {
$lte: 5
}
}
}, {
$project: {
value: {
$filter: {
input: "$value",
as: "value",
cond: { $lte: ["$$value.time", 5] }
}
}
}
}, {
$unwind: "$value"
}, {
$group: {
_id: "$_id",
time: { $max: "$value.time" },
characteristics: { $first: "$value.characteristics" }
}
})
Sample output :
{ "_id" : ObjectId("588a8c3080a14de2d654eb7b"), "time" : 4, "characteristics" : "pqrs" }
{ "_id" : ObjectId("588a89327fe89686fd2210b2"), "time" : 1, "characteristics" : "pqrs" }