db.find vs db.aggregation to select nested array Object - mongodb-query

Question

I'v tried to perform the following query :
db.getCollection('fxh').find({"username": "user1", "pf.acc.accnbr" : 915177},{userid: true, "pf.pfid": true, "pf.acc.accid":true})
and my collection is the following :
{
"_id" : ObjectId("5932fd8f381d4c0a7de21942"),
"userid" : 1496513894,
"username" : "user1",
"email" : "user1#gmail.com",
"fullname" : "User 1",
"pf" : {
"acc" : [
{
"cyc" : [
{
"det" : {
"status" : "New",
"dcycid" : 1496513941
},
"status" : "New",
"name" : "QPT202017_M1",
"cycid" : 1496513940
}
],
"status" : "New",
"accnbr" : 915177,
"accid" : 1496513939
},
{
"cyc" : [
{
"det" : {
"status" : "New",
"dcycid" : 1496552643
},
"status" : "New",
"name" : "QPT202017_S8",
"cycid" : 1496552642
}
],
"status" : "New",
"accnbr" : 73497,
"accid" : 1496552641
}
],
"pfid" : 1496513935,
},
"lastupdate" : ISODate("2017-06-03T18:18:55.080Z"),
"__v" : 0
}
When I execute the query the result is the following :
{
"_id" : ObjectId("5932fd8f381d4c0a7de21942"),
"userid" : 1496513894,
"portfolio" : {
"acc" : [
{
"accid" : 1496513939
},
{
"accid" : 1496552641
}
],
"pfid" : 1496513935
}
}
And my problem is that I need to see only the concerned accid and the result returns the all accid !.
Any idea how just to return the selected accid of accnbr ?
NB : I have also tried to add $ sign at the end of my query , it
selects the right acc but it returns the all objects or I need just
only ONE returned object.
On 6/5/17
I also used the aggregate command instead of find and it get result by using this :
db.getCollection('fxh').aggregate([ { $unwind : "$pf.acc"} , { $match : {"username":"adh1", "pf.acc.accbr": 915177 } }, {$project : {_id:0, accid: "$pf.acc.accid"}}])
But could NOT get a lower level result, when I ran this :
db.getCollection('fxh').aggregate([ { $unwind : "$pf.acc.cyc"} , { $match : {"username":"adh1", "pf.acc.accbr": 915177, "pf.acc.cyc.name": "QPT202017_M1" } }, {$project : {_id:0, cycid: "$pf.acc.cyc.cycid"}}])
Any idea ?

Answer 1

You can try the below aggregation pipeline.
The idea is to $unwind one nested level at a time, starting from the outermost to the innermost.
For each nested level unwinding, you can apply the$match to limit the documents and continue till you have the desired shape.
You can $group it together at the end to get back to the original shape.
db.getCollection('fxh').aggregate([
{ $match : {"username":"adh1"} },
{ $unwind : "$pf.acc"} ,
{ $match : {"pf.acc.accbr": 915177 } },
{ $unwind : "$pf.acc.cyc"},
{ $match : {"pf.acc.cyc.name": "QPT202017_M1" } },
{$project : {_id:0, accid: "$pf.acc.accid", cycid: "$pf.acc.cyc.cycid"}}])