Aggregate and grouping in Mongo - mongodb

Question

How do I get a summary count in Mongo. I have the following record structure and I would like to get a summary by date and status
{
"_id": "1",
"History": [
{
"id": "11",
"message": "",
"status": "send",
"resultCount": 0,
"createdDate": "",
"modifiedDate": ""
},
{
"id": "21",
"message": "",
"status": "skipped",
"resultCount": 0,
"createdDate": "",
"modifiedDate": ""
}
]
}
This is what I would like..
date x
status :
count : nn
This is my Mongo structure

Answer 1

Let's assume you have the following data in 'history' collection:
{
"_id": "1",
"History": [
{
"id": "21",
"message": "",
"status": "send",
"resultCount": 0,
"createdDate": "date1",
"modifiedDate": ""
},
{
"id": "22",
"message": "",
"status": "skipped",
"resultCount": 0,
"createdDate": "date1",
"modifiedDate": ""
},
{
"id": "23",
"message": "",
"status": "skipped",
"resultCount": 0,
"createdDate": "date2",
"modifiedDate": ""
},
{
"id": "24",
"message": "",
"status": "skipped",
"resultCount": 0,
"createdDate": "date2",
"modifiedDate": ""
}
]
}
You can design your query in the following way to get the desired summary.
db.history.aggregate([
{
$unwind:"$History"
},
{
$group:{
"_id":{
"createdDate":"$History.createdDate",
"status":"$History.status"
},
"createdDate":{
$first: "$History.createdDate"
},
"status":{
$first:"$History.status"
},
"count":{
$sum:1
}
}
},
{
$group:{
"_id":"$createdDate",
"createdDate":{
$first:"$createdDate"
},
"info":{
$push:{
"status":"$status",
"count":"$count"
}
}
}
},
{
$project:{
"_id":0
}
}
]).pretty()
It would result in the following:
{
"createdDate" : "date1",
"info" : [
{
"status" : "skipped",
"count" : 1
},
{
"status" : "send",
"count" : 1
}
]
}
{
"createdDate" : "date2",
"info" : [
{
"status" : "skipped",
"count" : 2
}
]
}
Aggregation stages details:
Stage I: The 'History' array is unwinded i.e. the array would be split and each element would create an individual document.
Stage II: The data is grouped on the basis of 'createdDate' and 'status'. In this stage, the count of status is also calculated.
Stage III: The data is further grouped on the basis of 'createdDate'
only
Stage IV: Eliminating non-required fields from the result