Need Help Join Collection - mongodb

Question

Collection Inventory sample data:
{
"_id" : "89011704252315531324",
"sku" : "A2015-01-000",
"type" : "package",
"status" : "active",
"lng" : "-72.789153",
"lat" : "44.173515",
"acq" : "28",
"gtime" : ISODate("2017-01-11T22:27:48.000Z"),
"qlng" : "-72.796501",
"qlat" : "44.214783",
"qtime" : ISODate("2016-11-27T18:21:10.000Z"),
"timestamp" : ISODate("2017-01-12T14:43:29.000Z"),
"modified" : Date(-62135596800000),
"battery" : "60",
"wearables" : [
{
"_id" : "0009003C100228234E45",
"type" : "wearable",
"status" : "active",
"battery" : "50",
"timestamp" : ISODate("2017-01-12T11:43:33.000Z")
},
{
"_id" : "004A003F200B36634E45",
"type" : "cradle",
"status" : "active",
"battery" : "64",
"timestamp" : ISODate("2017-01-11T22:27:26.000Z")
},
{
"_id" : "11223344556600000B55",
"type" : "falldetect",
"status" : "active",
"battery" : "64",
"timestamp" : ISODate("2017-01-12T08:43:29.000Z")
}
],
"company" : "ConnectAmericaProduction",
"companies" : [],
"remoteIp" : "172.31.45.196:53864",
"subscriber" : "5783e20aa2c89f346e000006",
"ring" : "90",
"speaker" : "90",
"mic" : "55",
"version" : "4352",
"cradle" : "OFF",
"ctime" : ISODate("2017-01-11T23:13:59.000Z"),
"csqtime" : Date(-62135596800000)
}
collection calllog sample data
{
"_id" : "89011704252315531324",
"cdr" : [
{
"direction" : "Outgoing",
"duration" : 46,
"timestamp" : ISODate("2016-11-23T03:25:06.000Z"),
"number" : "",
"name" : "Call Center",
"lng" : "-71.208061",
"lat" : "42.330265",
"acq" : "",
"timezone" : {
"dstOffset" : 0.0,
"rawOffset" : 0.0,
"status" : "",
"timeZoneId" : "",
"timeZoneName" : ""
}
},
{
"direction" : "Incoming",
"duration" : 51,
"timestamp" : ISODate("2016-11-23T03:26:02.000Z"),
"number" : "",
"name" : "Call Center",
"lng" : "-71.205727",
"lat" : "42.333347",
"acq" : "",
"timezone" : {
"dstOffset" : 0.0,
"rawOffset" : 0.0,
"status" : "",
"timeZoneId" : "",
"timeZoneName" : ""
}
},
{
"direction" : "Outgoing",
"duration" : 49,
"timestamp" : ISODate("2016-11-27T18:21:04.000Z"),
"number" : "",
"name" : "Call Center",
"lng" : "-72.796501",
"lat" : "44.214783",
"acq" : "",
"timezone" : {
"dstOffset" : 0.0,
"rawOffset" : -18000.0,
"status" : "OK",
"timeZoneId" : "America/New_York",
"timeZoneName" : "Eastern Standard Time"
}
}
]
}
after run this aggrgrate function
db.calllog.aggregate([{$unwind: "$cdr"}, {$lookup:{from: "inventory", localField: "_id", foreignField: "_id", as: "wearables" }}, { "$project": { "cdr.direction": 1, "cdr.duration": 1,"cdr.date": 1,"wearables.type": 1, "wearables.status": 1, "wearables.battery": 1} }])
Result:
{ "_id" : "89011704252315531324", "cdr" : { "direction" : "Outgoing", "duration" : 46 }, "wearables" : [ { "type" : "package", "status" : "active", "battery" : "60" } ] }
{ "_id" : "89011704252315531324", "cdr" : { "direction" : "Incoming", "duration" : 51 }, "wearables" : [ { "type" : "package", "status" : "active", "battery" : "60" } ] }
{ "_id" : "89011704252315531324", "cdr" : { "direction" : "Outgoing", "duration" : 49 }, "wearables" : [ { "type" : "package", "status" : "active", "battery" : "60" } ] }
needed help can not get query to shows wearables type such as wearable, cradle, falldetect
thank

Answer 1

Did you try to do wearables.wearables.type? When you call wearables.type, you are actually getting the type of the Inventory. If you need the type of the wearable that is inside the inventory. You need to put inventory.wearables.type. The initial problem is that you're calling the inventory "wearables" and making a confusion out of it.
I would do the following:
db.calllog.aggregate([{$unwind: "$cdr"},
{$lookup:{from: "inventory", localField: "_id", foreignField: "_id", as: "inventory" }},
{$unwind: "$inventory.wearables"},
{ "$project": {
"cdr.direction": 1,
"cdr.duration": 1,
"cdr.date": 1,
"inventory.type": 1,
"inventory.status": 1,
"inventory.battery": 1,
"inventory.wearables.type":1
}}])