Grouping and summing after using $addToSet in MongoDB - mongodb

Question

Assume I have the following data:
[{
"type" : "DIVIDEND_OR_INTEREST",
"netAmount" : 2.43,
"transactionDate" : "2019-01-01T17:02:36+0000",
"transactionId" : 1,
"transactionItem" : {
"instrument" : {
"symbol" : "SPHD"
}
}
},
{
"type" : "DIVIDEND_OR_INTEREST",
"netAmount" : 5.00,
"transactionDate" : "2019-01-01T17:02:36+0000",
"transactionId" : 2,
"transactionItem" : {
"instrument" : {
"symbol" : "ATT"
}
}
},
{
"type" : "DIVIDEND_OR_INTEREST",
"netAmount" : 2.43,
"transactionDate" : "2019-02-01T17:02:36+0000",
"transactionId" : 3,
"transactionItem" : {
"instrument" : {
"symbol" : "SPHD"
}
}
},
{
"type" : "DIVIDEND_OR_INTEREST",
"netAmount" : 5.00,
"transactionDate" : "2019-02-01T17:02:36+0000",
"transactionId" : 4,
"transactionItem" : {
"instrument" : {
"symbol" : "ATT"
}
}
}]
I want to group the data by year and get a total sum for that year. I also want an array of the items used during the group, grouped by a field and summed, if that makes sense. This is ultimately what I want to end up with:
{
"year": [
{
"year": "2019",
"totalYear": 14.86,
"dividends": [
{
"symbol": "T",
"amount": 10.00
},
{
"symbol": "SPHD",
"amount": 4.86
}
]
}
]
}
Below is the code I have written so far using Mongoose. The problem is that I can't figure out how to group and sum the items that I added to the set. I could always do that in the application layer but I was hoping to accomplish this entirely inside of a query.:
const [transactions] = await Transaction.aggregate([
{ $match: { type: TransactionType.DIVIDEND_OR_INTEREST, netAmount: { $gte: 0 } } },
{
$facet: {
year: [
{
$group: {
_id: { $dateToString: { format: '%Y', date: '$transactionDate' } },
totalYear: { $sum: '$netAmount' },
dividends: {
$addToSet: {
symbol: '$transactionItem.instrument.symbol',
amount: '$netAmount',
},
},
},
},
{ $sort: { _id: 1 } },
{
$project: {
year: '$_id',
totalYear: { $round: ['$totalYear', 2] },
dividends: '$dividends',
_id: false,
},
},
],
},
},
]).exec();

Answer 1

It requires to do two group stages,
First group by year and symbol
Second group by only year
If the transactionDate field has date type value then just use $year operator to get the year
I would suggest you do $sort after the immediate $match stage to use an index if you have created or planning for future
const [transactions] = await Transaction.aggregate([
{
$match: {
type: TransactionType.DIVIDEND_OR_INTEREST,
netAmount: { $gte: 0 }
}
},
{ $sort: { transactionDate: 1 } },
{
$facet: {
year: [
{
$group: {
_id: {
year: { $year: "$transactionDate" },
symbol: "$transactionItem.instrument.symbol"
},
netAmount: { $sum: "$netAmount" }
}
},
{
$group: {
_id: "$_id.year",
totalYear: { $sum: "$netAmount" },
dividends: {
$push: {
symbol: "$_id.symbol",
amount: "$netAmount"
}
}
}
},
{
$project: {
_id: 0,
year: "$_id",
totalYear: 1,
dividends: 1
}
}
]
}
}
]).exec();
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