MongoDB aggregation - group and retrieve ohters fileds - json

Question

i have a collection with this documents:
{
"_id" : BinData(3,"utMu84VFQk+p6LOEE3Ia3w=="),
"DepartDate" : ISODate("2017-08-14T02:00:00.000+02:00"),
"Origin" : {
"Code" : "MIL",
"City" : "Milano",
"Country" : "IT"
},
"Destination" : {
"Code" : "TIA",
"City" : "Tirana",
"Country" : "AL"
},
"ReturnDate" : ISODate("2017-08-21T18:05:00.000+02:00"),
"SearchDate" : ISODate("2017-07-15T02:00:00.000+02:00"),
"Duration" : 150,
"Price" : "376.79",
"PriceCents" : 37679,
"Currency" : "EUR",
},
{
"_id" : BinData(3,"utMu845468+p6Lertya3w=="),
"DepartDate" : ISODate("2017-08-14T02:00:00.000+02:00"),
"Origin" : {
"Code" : "AOI",
"City" : "Ancona",
"Country" : "IT"
},
"Destination" : {
"Code" : "TIA",
"City" : "Tirana",
"Country" : "AL"
},
"ReturnDate" : ISODate("2017-08-21T18:05:00.000+02:00"),
"SearchDate" : ISODate("2017-07-15T02:00:00.000+02:00"),
"Duration" : 100,
"Price" : "376.79",
"PriceCents" : 37679,
"Currency" : "EUR",
},
.........
.........
I want to group by ONLY Destination.City and return an object with
Destination.City, Destination.Code and count. Like this example:
/* 1 */
{
"_id" : {
"Code" : "PMO",
"City" : "Palermo",
"Country" : "IT"
},
"count" : 184564.0
},
/* 2 */
{
"_id" : {
"Code" : "CAG",
"City" : "Cagliari",
"Country" : "IT"
},
"count" : 130873.0
},
......
......
I tried with this query (i use MongoBooster):
db.parsed_data.aggregate([
{ "$match" : { "Destination.Country" : "IT", "Segments" : { "$elemMatch" : { "Carrier" : "AZ" } } } },
{ "$group" : { "_id" : { "City" : "$Destination.City"}, "count" : { "$sum" : 1 } } },
{ "$project" : {"Destination.Code" : 1, "Destination.City" : 1, "Destination.Country" : 1 }},
{ "$sort" : { "count" : -1 } },
{ "$limit" : 9 }])
It returns grouped by City but it shows only the City Name.
In this way:
/* 1 */
{
"_id" : {
"City" : "Lampedusa"
}
},
/* 2 */
{
"_id" : {
"City" : "Trieste"
}
},
This is not correct.
How can i group by ONLY the Destination.City and return an object with
Destination.City, Destination.Code and count?
Thx