How can I select all data based on date range mongoDB? - mongodb

Question

I have a lists of records like below
[
{
"product": "p1",
"salesdate": "2020-02-01",
"amount": 100
},
{
"product": "p2",
"salesdate": "2020-02-04",
"amount": 200
},
]
On 2nd feb and 3rd feb i don't have data. But I need to add this in my result. My expected result is
[
{
"amount": 100,
"salesdate": "2020-02-01"
},
{
"amount": 0,
"salesdate": "2020-02-02"
},
{
"amount": 0,
"salesdate": "2020-02-03"
}
{
"amount": 200,
"salesdate": "2020-02-04"
}
]
Can I achieve this using mongoDB?
https://mongoplayground.net/p/EiAJdY9jRHn

Answer 1

You can use $reduce for it. Whenever one has to work with data/time values, then I recommend the moment.js library. You don't have to use it, but it makes your life easier.
db.collection.aggregate([
// Put all data into one document
{ $group: { _id: null, data: { $push: "$$ROOT" } } },
// Add missing days
{
$addFields: {
data: {
$reduce: {
// Define the range of date
input: { $range: [0, moment().get('day')] },
initialValue: [],
in: {
$let: {
vars: {
ts: {
$add: [moment().startOf('month').toDate(), { $multiply: ["$$this", 1000 * 60 * 60 * 24] }]
}
},
in: {
$concatArrays: [
"$$value",
[{
$ifNull: [
{ $first: { $filter: { input: "$data", cond: { $eq: ["$$this.salesdate", "$$ts"] } } } },
// Default value for missing days
{ salesdate: "$$ts", amount: 0 }
]
}]
]
}
}
}
}
}
}
},
{ $unwind: "$data" },
{ $replaceRoot: { newRoot: "$data" } }
// If requried add further $group stages
])
Note, this code returns values from first day of current months to current day (not 2020 as in your sample data). You may adapt the ranges - your requirements are not clear from the question.
Mongo Playground