Filter by nested arrays/objects values (on different levels) and $push by multiple level - MongoDB Aggregate - mongodb

Question

I have a document with multiple level of embedded subdocument each has some nested array. Using $unwind and sort, do sorting based on day in descending and using push to combine each row records into single array. This Push is working only at one level means it allows only one push. If want to do the same things on the nested level and retains the top level data, got "errmsg" : "Unrecognized expression '$push'".
{
"_id" : ObjectId("5f5638d0ff25e01482432803"),
"name" : "XXXX",
"mobileNo" : 323232323,
"payroll" : [
{
"_id" : ObjectId("5f5638d0ff25e01482432801"),
"month" : "Jan",
"salary" : 18200,
"payrollDetails" : [
{
"day" : "1",
"salary" : 200,
},
{
"day" : "2",
"salary" : 201,
}
]
},
{
"_id" : ObjectId("5f5638d0ff25e01482432802"),
"month" : "Feb",
"salary" : 8300,
"payrollDetails" : [
{
"day" : "1",
"salary" : 300,
},
{
"day" : "2",
"salary" : 400,
}
]
}
],
}
Expected Result:
{
"_id" : ObjectId("5f5638d0ff25e01482432803"),
"name" : "XXXX",
"mobileNo" : 323232323,
"payroll" : [
{
"_id" : ObjectId("5f5638d0ff25e01482432801"),
"month" : "Jan",
"salary" : 18200,
"payrollDetails" : [
{
"day" : "2",
"salary" : 201
},
{
"day" : "1",
"salary" : 200
}
]
},
{
"_id" : ObjectId("5f5638d0ff25e01482432802"),
"month" : "Feb",
"salary" : 8300,
"payrollDetails" : [
{
"day" : "2",
"salary" : 400
},
{
"day" : "1",
"salary" : 300
}
]
}
],
}
Just day will be sorted and remaining things are same
I have tried but it got unrecognized expression '$push'
db.employee.aggregate([
{$unwind: '$payroll'},
{$unwind: '$payroll.payrollDetails'},
{$sort: {'payroll.payrollDetails.day': -1}},
{$group: {_id: '$_id', payroll: {$push: {payrollDetails:{$push:
'$payroll.payrollDetails'} }}}}])

Answer 1

It requires two time $group, you can't use $push operator two times in a field,
$group by main id and payroll id, construct payrollDetails array
$sort by payroll id (you can skip if not required)
$group by main id and construct payroll array
db.employee.aggregate([
{ $unwind: "$payroll" },
{ $unwind: "$payroll.payrollDetails" },
{ $sort: { "payroll.payrollDetails.day": -1 } },
{
$group: {
_id: {
_id: "$_id",
pid: "$payroll._id"
},
name: { $first: "$name" },
mobileNo: { $first: "$mobileNo" },
payrollDetails: { $push: "$payroll.payrollDetails" },
month: { $first: "$payroll.month" },
salary: { $first: "$payroll.salary" }
}
},
{ $sort: { "payroll._id": -1 } },
{
$group: {
_id: "$_id._id",
name: { $first: "$name" },
mobileNo: { $first: "$mobileNo" },
payroll: {
$push: {
_id: "$_id.pid",
month: "$month",
salary: "$salary",
payrollDetails: "$payrollDetails"
}
}
}
}
])
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