MongoDB aggregate $match and $group with $sum - mongodb

Question

i have a collection with documents like this:
{
"Company" : "4433",
"Descripcion" : "trabajo",
"Referencia" : "11817",
"HoraImportado" : "15:54",
"ImportedOd" : "2014-05-20T13:54:28.493Z",
"Items" : [],
"Notes" : [
{
"_id" : ObjectId("537b5ea4c61b1d1743f43420"),
"NoteDateTime" : "2014-05-20T13:54:44.418Z",
"Description" : "nota",
"IsForTechnician" : true,
"Username" : "admin"
},
{
"_id" : ObjectId("537c4a549e956f77ab8c7c38"),
"NoteDateTime" : ISODate("2014-05-21T06:40:20.299Z"),
"Description" : "ok",
"IsForTechnician" : true,
"Username" : "admin"
}
],
"OrderState" : "Review",
"SiniestroDe" : "Emergencia",
"Technicians" : [
{
"TechnicianId" : ObjectId("53465f9d519c94680327965d"),
"Name" : "Administrator",
"AssignedOn" : ISODate("2014-05-20T13:54:44.373Z"),
"RemovedOn" : null
}
],
"TechniciansHistory" : [
{
"TechnicianId" : ObjectId("53465f9d519c94680327965d"),
"Name" : "Administrator",
"AssignedOn" : ISODate("2014-05-20T13:54:44.373Z"),
"RemovedOn" : null
},
{
"Name" : "Nuevo",
"AssignedOn" : ISODate("2014-05-20T13:54:44.373Z"),
"RemovedOn" : null,
"TechnicianId" : ObjectId("5383577a994be8b9a9e3f01e")
}
],
"Telefonos" : "615554006",
"_id" : ObjectId("537b5ea4c61b1d1743f4341f"),
"works" : [
{
"code" : "A001",
"name" : "Cambiar bombilla",
"orderId" : "537b5ea4c61b1d1743f4341f",
"price" : "11",
"ID" : 33,
"lazyLoaded" : true,
"status" : 0,
"Date" : ISODate("2014-05-21T06:40:20.299Z"),
"TechnicianId" : "53465f9d519c94680327965d",
"_id" : ObjectId("537c4a549e956f77ab8c7c39")
},
{
"code" : "A001",
"name" : "Cambiar bombilla",
"orderId" : "537b5ea4c61b1d1743f4341f",
"price" : "11",
"ID" : 34,
"lazyLoaded" : true,
"status" : 0,
"Date" : ISODate("2014-05-21T06:40:20.299Z"),
"TechnicianId" : "53465f9d519c94680327965d",
"_id" : ObjectId("537c4a549e956f77ab8c7c3a")
}
]
}
Now i want to get the works for a selected TechnicianId array, group by TechnicianId and get the sum of the works.price for each technician.+
I try with this:
db.orders.aggregate([
{ $match: { 'works.TechnicianId': {$in:['53465f9d519c94680327965d']}}},
{ $group: { _id: "$works.TechnicianId",total:{$sum:'$works.price'}}},
])
And this is the result:
{
"result" : [
{
"_id" : [
"53465f9d519c94680327965d",
"53465f9d519c94680327965d"
],
"total" : 0
}
],
"ok" : 1
}
The total its the $sum but its 0 but should be 44.

Answer 1

Try adding unwind,
db.orders.aggregate([
{ $match: { 'works.TechnicianId': {$in:['53465f9d519c94680327965d']}}},
{ $unwind: "$works" },
{ $group: { _id: "$works.TechnicianId",total:{$sum:'$works.price'}}},
])
Look here for more info : http://docs.mongodb.org/manual/reference/operator/aggregation/unwind/

Answer 2

The price value is a string. $sum only operates on Numbers.
I've checked this by running the following:
db.foo.insert({"cost": "1"})
db.foo.insert({"cost": "2"})
db.foo.insert({"cost": "3"})
db.foo.insert({"cost": 4})
db.foo.insert({"cost": 5})
db.foo.aggregate([{$group: {_id: null, cost: {$sum: "$cost"}}}])
{ "result" : [ { "_id" : null, "cost" : 9 } ], "ok" : 1 }
According to this answer, you can't cast values in normal Mongo queries, so you can't change the string to a number inline.
You should either update all values to a Number datatype or use map-reduce. I'd go for the former.
If the value is a string to prevent floating point errors, consider multiplying by 100 to store the value in cents: "10.50" --> 1050
As Lalit Agarwal indicated, you'll also need to unwind the array of works. Example of what happens if you don't:
db.bar.insert({"works": [{price: 10}]})
db.bar.insert({"works": [{price: 20}, {price: 30}]})
db.bar.insert({"works": [{price: 40}, {price: 50}]})
db.bar.aggregate([
{$group: {_id: null, total: {$sum: "$works.price"} }}
])
{ "result" : [ { "_id" : null, "total" : 0 } ], "ok" : 1 }
db.bar.aggregate([
{$unwind: "$works"},
{$group: {_id: null, total: {$sum: "$works.price"} }}
])
{ "result" : [ { "_id" : null, "total" : 150 } ], "ok" : 1 }
What $unwind does is make 5 documents out of the initial 3, all with a single value in the works field. It then groups and sums them.

Answer 3

db.inventory.insert(
{
item: “ABC1”,
details: {
model: “14Q3”,
manufacturer: “XYZ Company”
},
stock: [ { size: “S”, qty: 25 }, { size: “M”, qty: 50 } ],
category: “clothing”
}
)