Aggregate query in MongoDB - mongodb

Question

I'm trying to create some daily stats from a MongoDB table. The document contains messages that have a create-date, state (Warn, Error, Complete). I'd like to product a query that results in one record per - Date,Count of Warn, Count of Error, Count of Complete. I'm a newbie with Mongo and just learning the query language. I've tried aggregation with mixed results:
db.TransactionLogs.aggregate(
{ $group : {
_id : {
category: {$substr:["$startDate",0,10]},
term: "$Status",
},
total: { $sum : 2 }
}
})
results in multiple records per date by status:
"result" : [
{
"_id" : {
"category" : "2015-02-10",
"term" : "Completed",
},
"total" : 532
},
{
"_id" : {
"category" : "2015-02-10",
"term" : "Error",
},
"total" : 616
},
Message:
{ "_id" : "2ceda481-3dd3-480d-800d-95288edce6f2", "MID" : "02de5194-7a1d-4854-922c-934902840136", "Status" : "Completed", "firstName" : "Willy", "lastName" : "Wire", "allocation" : "100", "initEvent" : "Marriage", "system" : "Oracle", "startDate" : "2015-02-06T19:03:34.237Z", "stopDate" : "2015-02-06T19:23:34.237Z", "plan" : "445-A" }
I'm sure that its a lack of understanding of aggregation on my part. Any help or direction is greatly appreciated!
I figured it out. I needed to look at how to "pivot" in Mongo. This works:
db.TransactionLogs.aggregate([ { $project: { startdate: {$substr:["$startDate",0,10]},
cnt_e1: { $cond: [ { $eq: [ "$Status", "Error" ] }, "$count", 1 ] },
cnt_e2: { $cond: [ { $eq: [ "$Status", "Warning" ] }, "$count", 1 ] },
cnt_e3: { $cond: [ { $eq: [ "$Status", "Completed" ] }, "$count", 1 ] },
} },
{ $group: { _id: "$startdate", cnt_e1: { $sum: "$cnt_e1" }, cnt_e2: { $sum: "$cnt_e2" }, cnt_e3: { $sum: "$cnt_e3" } } },
{ $sort: { _id: 1 } },

Answer 1

Here's the code...
db.TransactionLogs.aggregate([ { $project: { startdate: {$substr:["$startDate",0,10]},
cnt_e1: { $cond: [ { $eq: [ "$Status", "Error" ] }, "$count", 1 ] },
cnt_e2: { $cond: [ { $eq: [ "$Status", "Warning" ] }, "$count", 1 ] },
cnt_e3: { $cond: [ { $eq: [ "$Status", "Completed" ] }, "$count", 1 ] },
} },
{ $group: { _id: "$startdate", cnt_e1: { $sum: "$cnt_e1" }, cnt_e2: { $sum: "$cnt_e2" }, cnt_e3: { $sum: "$cnt_e3" } } },
{ $sort: { _id: 1 } },