MongoDB groupby query - mongodb

Question

I have colletions containing records like
{ "type" : "me", "tid" : "1" }
{ "type" : "me", "tid" : "1" }
{ "type" : "me", "tid" : "1" }
{ "type" : "you", "tid" : "1" }
{ "type" : "you", "tid" : "1" }
{ "type" : "me", "tid" : "2" }
{ "type" : "me", "tid" : "2"}
{ "type" : "you", "tid" : "2"}
{ "type" : "you", "tid" : "2" }
{ "type" : "you", "tid" : "2"}
I have want result like below
[
{"tid" : "1","me" : 3,"you": 2},
{"tid" : "2","me" : 2,"you": 3}
]
I have tried group and; aggregate queries doesn't get required result format.
below is the group query.
db.coll.group({
key: {tid : 1,type:1},
cond: { tid : { "$in" : [ "1","2"]} },
reduce: function (curr,result) {
result.total = result.total + 1
},
initial: { total : 0}
})
it result is like
[
{"tid" : "1", "type" : "me" ,"total": 3 },
{"tid" : "1","type" : "you" ,"total": 2 },
{"tid" : "2", "type" : "me" ,"total": 2 },
{"tid" : "2","type" : "you" ,"total": 3 }
]
following is aggregate query
db.coll.aggregate([
{$match : { "tid" : {"$in" : ["1","2"]}}},
{$group : { _id : {tid : "$tid",type : "$type"},total : {"$sum" : 1}}}
])
gives following result
{
"result" :
[
{"_id" : {"tid" : "1","type" : "me"},"total" : 3},
{"_id" : {"tid" : "2","type" : "me" },"total" : 2},
{"_id" : {"tid" : "2","type" : "you"},"total" : 3}
]
"ok" : 1
}
it is possible to obtain I specified result or I have to do some manipulation in my code.
Thanks

Answer 1

If you change your aggregation to this:
db.so.aggregate([
{ $match : { "tid" : { "$in" : ["1", "2"] } } },
{ $group : {
_id : { tid : "$tid", type : "$type" },
total : { "$sum" : 1 }
} },
{ $group : {
_id : "$_id.tid",
values: { $push: { type: "$_id.type", total: '$total' } }
} }
])
Then your output is:
{
"result" : [
{
"_id" : "1",
"values" : [
{ "type" : "you", "total" : 2 },
{ "type" : "me", "total" : 3 }
]
},
{
"_id" : "2",
"values" : [
{ "type" : "me", "total" : 2 },
{ "type" : "you", "total" : 3 }
]
}
],
"ok" : 1
}
Although that is not the same as what you want, it is going to be the closest that you can get. And in your application, you can easily pull out the values in the same was as with what you would like to get out of it.
Just keep in mind, that in general you can not promote a value (you, me) to a key — unless your key is of a limited set (3-4 items max).