$divide elements of Embedded Documents - MongoDB Aggregation - mongodb

Question

I am trying to create an aggregation MongoDB query.
Structure of data:
{
"object_name": Example,
"values": [ {"name":"value1", "value":1},
{"name":"value2", "value":10},
{"name":"total", "value":105}
}
Goal: Find object names where value1/total > 0.5 and value2/total > 0.25 and total > 100.
The data is structured in this way to provide indexes on the value_name and value fields.
What I tried - aggregate with the following pipelines:
$match: filter documents with total > 100:
$match: { values: { $elemMatch: { value_name: "total", value: {$gte: 100 }
$project: grab only the value_names that we need (there are close to 200 different names)
$project: {
values: {
$filter: {
input: "$values",
as: "value",
cond: { $or: [
{ $eq: [ "$$value.name", "name1"] },
{ $eq: [ "$$value.name", "name2"] },
{ $eq: [ "$$value.name", "total"] },
] }
}
},
name: 1
}
then, { $unwind: "$values" }
And here, I could $group to $divide: name1/total, name2/total however I'm stuck on how to get those values.
I can't simply do stats.value: because it does not know which value I'm referring to. I believe $group can't do $elemMatch to also match the name.
If there are simpler solutions that this, I'd greatly appreciate your input.

Answer 1

Please try this :
We're filtering documents where values array has an object with
name : total & value > 100.
Adding object with name : total
to document.
Leaving only objects that match with criteria
value1/total > 0.5 and value2/total > 0.25 in values array.
If
size of that array is greater than 1, then those two conditions are
met.
Finally projecting only object_name
Query :
db.yourCollectionName.aggregate([{ $match: { values: { $elemMatch: { name: "total", value: { $gte: 100 } } } } },
{
$addFields: {
totalValue: {
$arrayElemAt: [{
$filter: {
input: "$values",
as: "item",
cond: { $eq: ["$$item.name", 'total'] }
}
}, 0]
}
}
},
{
$project: {
values: {
$filter: {
input: "$values",
as: "value",
cond: {
$or: [
{ $cond: [{ $eq: ["$$value.name", "value1"] }, { $gt: [{ $divide: ["$$value.value", '$totalValue.value'] }, 0.5] }, false] },
{ $cond: [{ $eq: ["$$value.name", "value2"] }, { $gt: [{ $divide: ["$$value.value", '$totalValue.value'] }, 0.25] }, false] }
]
}
}
}, object_name: 1
}
}, {
$match: {
$expr: { $gt: [{ $size: "$values" }, 1] }
}
}, { $project: { object_name: 1, _id: 0 } }])
Collection Data :
/* 1 */
{
"_id" : ObjectId("5e20bd94d02e05b694d55fa5"),
"object_name" : "Example",
"values" : [
{
"name" : "value1",
"value" : 1
},
{
"name" : "value2",
"value" : 10
},
{
"name" : "total",
"value" : 105
},
{
"name" : "total1",
"value" : 105
}
]
}
/* 2 */
{
"_id" : ObjectId("5e20bdb1d02e05b694d56490"),
"object_name" : "Example2",
"values" : [
{
"name" : "value1",
"value" : 1
},
{
"name" : "value2",
"value" : 10
},
{
"name" : "total",
"value" : 5
},
{
"name" : "total1",
"value" : 5
}
]
}
/* 3 */
{
"_id" : ObjectId("5e20d1b7d02e05b694d7c57a"),
"object_name" : "Example3",
"values" : [
{
"name" : "value1",
"value" : 100
},
{
"name" : "value2",
"value" : 100
},
{
"name" : "total",
"value" : 200
},
{
"name" : "total1",
"value" : 205
}
]
}
/* 4 */
{
"_id" : ObjectId("5e20d1cad02e05b694d7c71c"),
"object_name" : "Example4",
"values" : [
{
"name" : "value1",
"value" : 200
},
{
"name" : "value2",
"value" : 40
},
{
"name" : "total",
"value" : 200
},
{
"name" : "total1",
"value" : 205
}
]
}
/* 5 */
{
"_id" : ObjectId("5e20d1e2d02e05b694d7c933"),
"object_name" : "Example5",
"values" : [
{
"name" : "value1",
"value" : 150
},
{
"name" : "value2",
"value" : 100
},
{
"name" : "total",
"value" : 200
},
{
"name" : "total1",
"value" : 205
}
]
}
Result :
/* 1 */
{
"object_name" : "Example5"
}

Answer 2

You may convert your array into object with $arrayToObject operator and add tmp field to have easy access to value1, value2, total values
db.collection.aggregate([
{
$addFields: {
tmp: {
$arrayToObject: {
$map: {
input: "$values",
as: "value",
in: {
k: "$$value.name",
v: "$$value.value"
}
}
}
},
name: 1
}
},
{
$match: {
$expr: {
$and: [
{
$gt: [
{
$divide: [
"$tmp.value1",
"$tmp.total"
]
},
0.5
]
},
{
$gt: [
{
$divide: [
"$tmp.value2",
"$tmp.total"
]
},
0.25
]
},
{
$gt: [
"$tmp.total",
100
]
}
]
}
}
},
{
$project: {
tmp: 0
}
}
])
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