mongodb aggregation with array - mongodb

Question

I have data like this:
{
"_id" : ObjectId("..."),
"name" : "Entry 1",
"time" : ISODate("2013-12-28T06:00:00.000Z"),
"value" : 100
},
{
"_id" : ObjectId("..."),
"name" : "Entry 2",
"time" : ISODate("2013-12-28T06:00:00.000Z"),
"value" : 200
},
{
"_id" : ObjectId("..."),
"name" : "Entry 1",
"time" : ISODate("2013-12-28T11:00:00.000Z"),
"value" : 110
},
{
"_id" : ObjectId("..."),
"name" : "Entry 2",
"time" : ISODate("2013-12-28T11:00:00.000Z"),
"value" : 230
},
{
"_id" : ObjectId("..."),
"name" : "Entry 3",
"time" : ISODate("2013-12-28T11:00:00.000Z"),
"value" : 25
},
{
"_id" : ObjectId("..."),
"name" : "Entry 4",
"time" : ISODate("2013-12-28T11:00:00.000Z"),
"value" : 15
}
I need the result grouped by time with percentage for each entry like this (group entries by volume "others" when entries for time period more than two, but it's not necessary):
{
"_id": ISODate("2013-12-28T11:00:00.000Z"),
"entries": [
{
"name": "Entry 1",
"percentage": 33.3
},
{
"name": "Entry 2",
"percentage": 66.6
},
]
},
{
"_id": ISODate("2013-12-28T06:00:00.000Z"),
"entries": [
{
"name": "Entry 1",
"percentage": 28.9
},
{
"name": "Entry 2",
"percentage": 60.5
},
{
"name": "Others",
"percentage": 10.5
}
]
}
So the request I was try:
db.collection.aggregate([
{
"$addFields": {
"full_datetime": {"$substr": ["$time", 0, 19]}
}
},
{
"$group": {
"_id": "$full_datetime",
"value_sum": {"$sum": "$value"},
"entries": {
"$push": {
"name": "$name",
"percentage": {
"$multiply": [{
"$divide": ["$value", {"$literal": "$value_sum" }]
}, 100 ]
}
}
}
}
}
])
This request is not work because $value_sum does not exists inside $push.
Please help me how I can to send this $value_sum into the $push statement

Answer 1

You can use one more stage to calculate percentage using $map as,
db.collection.aggregate([
"$addFields": {
"full_datetime": {
"$substr": ["$time", 0, 19]
}
}
}, {
"$group": {
"_id": "$full_datetime",
"value_sum": {
"$sum": "$value"
},
"entries": {
"$push": {
"name": "$name",
"value": "$value"
}
}
}
}, {
"$project": {
"entriesNew": {
"$map": {
"input": "$entries",
"as": "entry",
"in": {
"name": "$$entry.name",
"percentage": {
"$multiply": [{
"$divide": ["$$entry.value", "$value_sum"]
}, 100]
}
}
}
}
}
}])
Output:
/* 1 */
{
"_id" : "2013-12-28T11:00:00",
"entries" : [
{
"name" : "Entry 1",
"percentage" : 28.9473684210526
},
{
"name" : "Entry 2",
"percentage" : 60.5263157894737
},
{
"name" : "Entry 3",
"percentage" : 6.57894736842105
},
{
"name" : "Entry 4",
"percentage" : 3.94736842105263
}
]
}
/* 2 */
{
"_id" : "2013-12-28T06:00:00",
"entries" : [
{
"name" : "Entry 1",
"percentage" : 33.3333333333333
},
{
"name" : "Entry 2",
"percentage" : 66.6666666666667
}
]
}