Could not get the number of counts using MongoDB and Node.js - node.js

Question

I need query to fetch the total count as per key value of document by matching some value from array using MongoDB. I am explaining my document and Input below.
dataArr=[
{'login_id':9937229853,'location':'Delhi'},
{'login_id':9937229854,'location':'JK'}
]
My document is given below.
feedback:
{
login_id:9937229853,
code: PTP,
remark:'Hello'
},
{
login_id:9937229853,
code: PTP,
remark:'Hii'
},
{
login_id:9937229853,
code: CB,
remark:'aaaaa'
},
{
login_id:9937229854,
code: PTP,
remark:'jjjjj'
},
{
login_id:9937229854,
code: CB,
remark:'dddd'
}
The above is my collection. Here I need as per user input login_id present inside array will match with document and the total count will be fetch as per document key and value. My expected output is given below. I am explaining my code below.
for(var i=0;i<dataArr.length;i++){
var login=dataArr[i]['login_id'];
//console.log('cdocs',dataArr[i]['login_id']);
Feedback.collection.count({login_id:dataArr[i]['login_id']},function(cerr,cdocs){
console.log('cdocs',login);
if (!cerr) {
if(cdocs > 0){
// console.log('login',cdocs);
db.collection.aggregate([
{
$match: {
keywords: { $not: {$size: 0} }
}
},
{ $unwind: "$keywords" },
{
$group: {
_id: {$toLower: '$keywords'},
count: { $sum: 1 }
}
},
{
$match: {
login_id: login
}
}
])
.toArray((err,docs)=>{
if (!err) {
// console.log('count::',docs);
finalArr=docs;
}
})
}
}
})
}
var data={'status':'success','data':finalArr}
res.send(data);
I need the expected result like below.
finalArr=[
{'login_id':9937229853,'location':'Delhi','PTP':2,'CB':1,'remark':3},
{'login_id':9937229854,'location':'JK','PTP':1,'CB':1,'remark':2},
]
But using my code I am getting the blank output. Please help me to resolve this issue.

Answer 1

You can do all this with a single aggregate operation. The first pipeline stage would be filtering the documents in the collection using the input array. You would need to map that array to just a list of ids though in order to use the $in query operator i.e.
const ids = dataArr.map(({ login_id }) => login_id)
which can then be used in the $match pipeline as
const match = { '$match': { 'login_in': { '$in': ids } } }
The next pipeline step will then use the $group stage to group the above filtered documents by the login_id key
const allGroup = { '$group': {
'_id': {
'login_id': '$login_id',
'code': '$code',
'remark': '$remark'
},
'count': { '$sum': 1 }
} }
Another $group pipeline stage to get the remarks counts as a list of key/value documents
const remarksGroup = { '$group': {
'_id': {
'login_id': '$_id.login_id',
'code': '$_id.code'
},
'remarks': {
'$push': {
'k': '$_id.remark',
'v': '$count'
}
},
'count': { '$sum': 1 }
} }
Get the code counts with a similar structure as above
const codeGroup = { '$group': {
'_id': '$_id.login_id',
'codes': {
'$push': {
'k': '$_id.code',
'v': '$count'
}
},
'remarks': { '$first': '$remarks' }
} }
You would need a final pipeline to convert the key/value pairs arrays to objects using $arrayToObject, merge the objects into one using $mergeObjects and replace the root document with the merged docs using $replaceRoot:
const projections = { '$replaceRoot': {
'newRoot': {
'$mergeObjects': [
{ 'login_id': '$_id' },
{ '$arrayToObject': '$codes' },
{ '$arrayToObject': '$remarks' }
]
}
} }
Your full aggregate pipeline operation would be:
(async () => {
try {
const ids = dataArr.map(({ login_id }) => login_id)
const match = { '$match': { 'login_in': { '$in': ids } } }
const allGroup = { '$group': {
'_id': {
'login_id': '$login_id',
'code': '$code',
'remark': '$remark'
},
'count': { '$sum': 1 }
} }
const remarksGroup = { '$group': {
'_id': {
'login_id': '$_id.login_id',
'code': '$_id.code'
},
'remarks': {
'$push': {
'k': '$_id.remark',
'v': '$count'
}
},
'count': { '$sum': 1 }
} }
const codeGroup = { '$group': {
'_id': '$_id.login_id',
'codes': {
'$push': {
'k': '$_id.code',
'v': '$count'
}
},
'remarks': { '$first': '$remarks' }
} }
const projections = { '$$replaceRoot': {
'newRoot': {
'$mergeObjects': [
{ 'login_id': '$_id' },
{ '$arrayToObject': '$codes' },
{ '$arrayToObject': '$remarks' }
]
}
} }
const result = await Feedback.aggregate([
match,
allGroup,
remarksGroup,
codeGroup,
projections
])
/* get the location key */
const data = result.map(item => {
const [{ location }, ...rest] = dataArr.filter(d => d.location_id === item.location_id)
return { location, ...item }
})
console.log(data)
res.send(data)
} catch (err) {
// handle error
}
})()