Aggregate Field Values to Separate Key Names - mongodb

Question

I have a collection in MongoDB with sample data something like this (simplified):
{
_id: 1,
username: "ted",
content: "4125151",
status: "complete"
}
{
_id: 2,
username: "sam",
content: "4151",
status: "new"
}
{
_id: 3,
username: "ted",
content: "511",
status: "new"
}
{
_id: 4,
username: "ted",
content: "411",
status: "in_progress"
}
{
_id: 5,
username: "pat",
content: "1sds51",
status: "complete"
}
{
_id: 6,
username: "ted",
content: "4151",
status: "in_progress"
}
{
_id: 7,
username: "ted",
content: "4125",
status: "in_progress"
}
I need to aggregate the data such that for each user, I get a count for each status value as well as a total number of records. The result should look like this:
[
{
username: “pat”,
new: 0,
in_progress: 0,
complete: 1,
total: 1
},
{
username: “sam”,
new: 1,
in_progress: 0,
complete: 0,
total: 1
},
{
username: “ted”,
new: 1,
in_progress: 3,
complete: 1,
total: 5
}
]
Or any format that will effectively serve the same purpose which is, I want to be able to use with ngRepeat to display on the front end in this format:
User New In Progress Complete Total
pat 0 0 1 1
sam 1 0 0 1
ted 1 3 1 5
I can perform this aggregation:
{
"$group": {
"_id": {
"username": "$username",
"status": "$status"
},
"count": {
"$sum": 1
}
}
}
This gives me the individual count for each user/status combination that has at least one record. But then I have to piece it together to get it in the format that I can use on the front end. This is not at all ideal.
Is there a way to perform the aggregation to get the data in the format that I need?

Answer 1

What you want is a "conditional" aggregation of the values to produce a distinct field property for each status.
This is pretty simple to do using the $cond operator:
[
{ "$group": {
"_id": "$username",
"new": { "$sum": { "$cond": [{ "$eq": [ "$status", "new" ] },1,0 ] } },
"complete": { "$sum": { "$cond": [{ "$eq": [ "$status", "complete" ] },1,0 ] } },
"in_progress": { "$sum": { "$cond": [{ "$eq": [ "$status", "in_progress" ] },1,0 ] } },
"total": { "$sum": 1 }
}}
]
Presuming of course those are the only "status" values, but if they are not then just add an additional $project to sum the fields you want:
[
{ "$match": { "status": { "$in": [ "new", "complete", "in_progress" ] } } },
{ "$group": {
"_id": "$username",
"new": { "$sum": { "$cond": [{ "$eq": [ "$status", "new" ] },1,0 ] } },
"complete": { "$sum": { "$cond": [{ "$eq": [ "$status", "complete" ] },1,0 ] } },
"in_progress": { "$sum": { "$cond": [{ "$eq": [ "$status", "in_progress" ] },1,0 ] } }
}},
{ "$project": {
"new": 1,
"complete": 1,
"in_progress": 1,
"total": { "$add": [ "$new", "$complete", "$in_progress" ] }
]
Or just include that $add within the $group with the same calculations for the separate fields. But the $match is probably just the best idea if there are indeed other status values you don't want.

Answer 2

Another answer using $group twice and a $push, In this below query you need to compute the final total on UI side.
db.collection.aggregate([
{
"$group": {
"_id": {
"username": "$username",
"status": "$status"
},
"statuscount": {
"$sum": 1
}
}
},
{
"$group": {
"_id": "$_id.username",
"finalstatus": {
"$push": {
"Status": "$_id.status",
"statuscount": "$statuscount"
}
}
}
}
])