How to do double group and push with two fields in MongoDB? - mongodb

Question

I have data like this:
[
{
"channel": "abc",
"date": "2019-01-01",
"revenue": 100,
"quantity": 100,
},
{
"channel": "xyz",
"date": "2019-02-10",
"revenue": 100,
"quantity": 100,
},
{
"channel": "def",
"date": "2020-01-01",
"revenue": 100,
"quantity": 100,
},
{
"channel": "abc",
"date": "2021-06-01",
"revenue": 100,
"quantity": 100,
},
{
"channel": "abc",
"date": "2021-06-12",
"revenue": 100,
"quantity": 100,
}
]
I want to group by channel and push data and again group by date (in month and year only) and push data and add a field after these pushes. The dates are all Date objects, not Strings. The avg_revenue is tot_revenue divided by tot_quantity.
[
{
"channel": "abc",
"dates": [
{
"date": "2019-01",
"totals": {
"tot_revenue": 100,
"tot_quantity": 100,
"avg_revenue": 1,
}
},
{
"date": "2019-01",
"totals": {
"tot_revenue": 200,
"tot_quantity": 200,
"avg_revenue": 1,
}
}
]
},
{
"channel": "def",
"dates": [
{
"date": "2020-01",
"totals": {
"tot_revenue": 100,
"tot_quantity": 100,
"avg_revenue": 1,
}
}
]
},
{
"channel": "xyz",
"dates": [
{
"date": "2019-02",
"totals": {
"tot_revenue": 100,
"tot_quantity": 100,
"avg_revenue": 1,
}
}
]
},
]
My attempt:
db.collection.aggregate([
{
"$set": {
"date": {
"$dateFromString": {
"dateString": "$date",
"format": "%Y-%m-%d"
}
}
}
},
{
$group: {
_id: {
channel: "$channel",
month: {
$month: "$date"
},
year: {
$year: "$date"
}
},
report_dates: {
$push: {
report_date: "$date",
revenue: "$revenue",
quantity: "$quantity",
}
},
}
},
{
$group: {
_id: {
month: "$month",
year: "$year",
},
values: {
$push: {
revenue: "$revenue",
quantity: "$quantity",
}
},
}
}
])

Answer 1

You need to create an aggregation pipeline that consists of two $group steps, the first to group all the documents by the channel and date fields whilst accumulating the tot_revenue and tot_quantity aggregates. The other $group stage will compute the dates list with the totals.
The following pipeline should give the desired output:
db.collection.aggregate([
{ '$group': {
'_id': {
'channel': '$channel',
'date': {
'$dateToString': {
'format': "%Y-%m", 'date': {
"$dateFromString": {
"dateString": "$date",
"format": "%Y-%m-%d"
}
}
}
}
},
'tot_revenue': { '$sum': '$revenue' },
'tot_quantity': { '$sum': '$quantity' },
} },
{ '$group': {
'_id': '$_id.channel',
'dates': {
'$push': {
'date': '$_id.date',
'totals': {
'tot_revenue': '$tot_revenue',
'tot_quantity': '$tot_quantity',
'avg_revenue': { '$divide': ['$tot_revenue','$tot_quantity'] }
}
}
}
} }
])