Group based on discrete date ranges - mongodb

Question

I am new to MongoDB and I've been struggling to get a specific query to work without any luck.
I have a collection with millions of documents having a date and an amount, I want to get the aggregations for specific periods of time.
For example, I want to get the count, amount summations for the periods between 1/1/2015 - 15/1/2015 and between 1/2/2015 - 15/2/2015
A sample collection is
{ "_id" : "148404972864202083547392254", "account" : "3600", "amount" : 50, "date" : ISODate("2017-01-01T12:02:08.642Z")}
{ "_id" : "148404972864202085437392254", "account" : "3600", "amount" : 50, "date" : ISODate("2017-01-03T12:02:08.642Z")}
{ "_id" : "148404372864202083547392254", "account" : "3600", "amount" : 70, "date" : ISODate("2017-01-09T12:02:08.642Z")}
{ "_id" : "148404972864202083547342254", "account" : "3600", "amount" : 150, "date" : ISODate("2017-01-22T12:02:08.642Z")}
{ "_id" : "148404922864202083547392254", "account" : "3600", "amount" : 200, "date" : ISODate("2017-02-02T12:02:08.642Z")}
{ "_id" : "148404972155502083547392254", "account" : "3600", "amount" : 30, "date" : ISODate("2017-02-7T12:02:08.642Z")}
{ "_id" : "148404972864202122254732254", "account" : "3600", "amount" : 10, "date" : ISODate("2017-02-10T12:02:08.642Z")}
for date ranges between 1/1/2017 - 10/10/2017 and 1/2/2017 - 10/2/2017 the output would be like this:
1/1/2017 - 10/1/2017 - count =3, amount summation: 170
10/2/2017 - 15/2/2017 - count =2, amount summation: 40
Is it possible to work with such different date ranges? The code would be in Java, but as an example in mongo, can someone please help me?

Answer 1

There must be a more elegant solution than this. Anyways you can wrap it into a function and generalize date related arguments.
First, you need to make a projection at the same time deciding into which range an item goes (note the huge $switch expression). By default, an item goes into 'null' range.
Then, you filter out results that didn't match your criteria (i.e. range != null).
The very last step is to group items by the range and make all needed calculations.
db.items.aggregate([
{ $project : {
amount : true,
account : true,
date : true,
range : {
$switch : {
branches : [
{
case : {
$and : [
{ $gte : [ "$date", ISODate("2017-01-01T00:00:00.000Z") ] },
{ $lt : [ "$date", ISODate("2017-01-10T00:00:00.000Z") ] }
]
},
then : { $concat : [
{ $dateToString: { format: "%d/%m/%Y", date: ISODate("2017-01-01T00:00:00.000Z") } },
{ $literal : " - " },
{ $dateToString: { format: "%d/%m/%Y", date: ISODate("2017-01-10T00:00:00.000Z") } }
] }
},
{
case : {
$and : [
{ $gte : [ "$date", ISODate("2017-02-01T00:00:00.000Z") ] },
{ $lt : [ "$date", ISODate("2017-02-10T00:00:00.000Z") ] }
]
},
then : { $concat : [
{ $dateToString: { format: "%d/%m/%Y", date: ISODate("2017-02-01T00:00:00.000Z") } },
{ $literal : " - " },
{ $dateToString: { format: "%d/%m/%Y", date: ISODate("2017-02-10T00:00:00.000Z") } }
] }
}
],
default : null
}
}
} },
{ $match : { range : { $ne : null } } },
{ $group : {
_id : "$range",
count : { $sum : 1 },
"amount summation" : { $sum : "$amount" }
} }
])
Based on your data it will give the following results*:
{ "_id" : "01/02/2017 - 10/02/2017", "count" : 2, "amount summation" : 230 }
{ "_id" : "01/01/2017 - 10/01/2017", "count" : 3, "amount summation" : 170 }
*I believe you have few typos in your questions, that's why the data look different.