MongoDB - Aggregate: How to group by depending on query - mongodb

Question

I want to aggregate over a collection where a type is given. The types come from query string and the can be day, month or year. Depending on what type the users chooses I want to group by.
For example: If the user chooses "month" I want to group by month.
Event.aggregate([
{
$lookup: { from: Product.collection.name, localField: 'product', foreignField: '_id', as: 'product' }
},
{
$group: {
_id: { $month: { date: "$date" } },
price: { $sum: "$price" },
result: { $mergeObjects: { name: "$product.name", _id: "$product._id" } },
count: { $sum: 1 }
},
},
]).then(response => {
console.log(response)
res.send(response)
})
I can not figure it out how to find a clean solution.
So far the only way I found was to use if conditional before Model.aggregate([])...
if (req.query.dateAvailability && req.query.dateAvailability === 'month') {
Event.aggregate([
{
$lookup: { from: Product.collection.name, localField: 'product', foreignField: '_id', as: 'product' }
},
{
$group: {
_id: { $month: { date: "$date" } },
price: { $sum: "$price" },
result: { $mergeObjects: { name: "$product.name", _id: "$product._id" } },
count: { $sum: 1 }
},
},
]).then(response => {
console.log(response)
res.send(response)
})
} else if (req.query.dateAvailability && req.query.dateAvailability === 'day') {
Event.aggregate([
{
$lookup: { from: Product.collection.name, localField: 'product', foreignField: '_id', as: 'product' }
},
{
$group: {
_id: { $dateToString: { format: "%d-%m-%Y", date: "$date" } },
price: { $sum: "$price" },
result: { $mergeObjects: { name: "$product.name", _id: "$product._id" } },
count: { $sum: 1 }
},
},
]).then(response => {
console.log(response)
res.send(response)
})
} else if (req.query.dateAvailability && req.query.dateAvailability === 'year') {
Event.aggregate([
{
$lookup: { from: Product.collection.name, localField: 'product', foreignField: '_id', as: 'product' }
},
{
$group: {
_id: { $year: { date: "$date" } },
price: { $sum: "$price" },
result: { $mergeObjects: { name: "$product.name", _id: "$product._id" } },
count: { $sum: 1 }
},
},
]).then(response => {
console.log(response)
res.send(response)
})
}
Model Event:
const EventSchema = new Schema({
client: {
type: [{
type: Schema.Types.ObjectId,
ref: 'Client'
}]
},
product: {
type: [{
type: Schema.Types.ObjectId,
ref: 'Product'
}]
},
date: {
type: Date,
maxlength: 64,
lowercase: true,
trim: true
},
place: {
type: String,
maxlength: 1200,
minlength: 1,
},
price: {
type: Number
},
comment: {
type: String,
maxlength: 12000,
minlength: 1,
},
status: {
type: Number,
min: 0,
max: 1,
default: 0,
validate: {
validator: Number.isInteger,
message: '{VALUE} is not an integer value'
}
},
},
{
toObject: { virtuals: true },
toJSON: { virtuals: true }
},
{
timestamps: true
},
);

Answer 1

There's no magic solution to remove the use of logic, In cases like this it will always be required.
However we can make the code a little sexier:
let groupCond;
if (req.query.dateAvailability && req.query.dateAvailability === 'month') {
groupCond = { $month: { date: "$date" } };
} else if (req.query.dateAvailability && req.query.dateAvailability === 'day') {
groupCond = { $dateToString: { format: "%d-%m-%Y", date: "$date" } };
} else if (req.query.dateAvailability && req.query.dateAvailability === 'year') {
groupCond = { $year: { date: "$date" } };
}
Event.aggregate([
{
$lookup: { from: Product.collection.name, localField: 'product', foreignField: '_id', as: 'product' }
},
{
$group: {
_id: groupCond,
price: { $sum: "$price" },
result: { $mergeObjects: { name: "$product.name", _id: "$product._id" } },
count: { $sum: 1 }
},
},
]).then(response => {
console.log(response)
res.send(response)
})

Answer 2

There is no magic bullet to your problem the logic has to happen somewhere. Either with an if statement outside the query or a $switch operator inside the query if you are using a version of mongodb 3.4 or greater.
{"$group": {
"_id":{
"$switch": {
"branches": [
{ "case":{ "$eq": [ { "$literal": "day" }, { "$literal": req.query.dateAvailability } ] },
"then": { $dateToString: { format: "%d-%m-%Y", date: "$date" } } },
{ "case":{ "$eq": [ { "$literal": "month" }, { "$literal": req.query.dateAvailability } ] },
"then": { $month: { date: "$date" } } },
{ "case":{ "$eq": [ { "$literal": "year" }, { "$literal": req.query.dateAvailability } ] },
"then": { $year: { date: "$date" } } }
],
"default": { ... default logic for when dateAvailability isn't set ... }
}
}
... rest of the group operation
} }