Where and Group By Using Moongose API MongoDB - mongodb

Question

I have written an aggregation function which will count the Message. Based on Message Status.
exports.countRecords = function(req, res) {
Message.aggregate([{
$group: {
_id: "$message_status",
count: {
$sum: 1
}
}
}, {
$sort: {
_id: 1
}
}], function(err, result) {
if (err) {
console.log(err);
return;
}
console.log(result);
res.jsonp(result);
});
};
Now i need to add a condition to count only when the channel_message_ID and channel_thread_Id are equal so i have modified the logic like below:
Message.aggregate([{
$match: {
channel_message_ID: { $eq: ["$channel_message_ID", "$channel_thread_Id"]}
}},
{$group: {
_id: "$message_status",
count: {
$sum: 1
}
},
}, {
$sort: {
_id: 1
}
}], function(err, result) {
if (err) {
console.log(err);
return;
}
console.log(result);
res.jsonp(result);
});
};
It is not at all working. Thanks in Advance.

Answer 1

try below solution:
$project:
Message.aggregate([{
{"$project": {
"channel_message_ID":1,
"channel_thread_Id":1,
"message_status": 1,
"cond": {"$eq":["$channel_message_ID","$channel_thread_Id"]}
}
},
{"$match":{"cond": true}},
{$group: {
_id: "$message_status",
count: {
$sum: 1
}
},
}, {
$sort: {
_id: 1
}
}], function(err, result) {
if (err) {
console.log(err);
return;
}
console.log(result);
res.jsonp(result);
});

Answer 2

You'll need to add a new field to the document at the first stage of the aggregation pipeline, this can be done by using the [$addFields]
(https://docs.mongodb.com/manual/reference/operator/aggregation/addFields/) stage
{ "$addFields" : { "idMatch" : { "$eq" : [ "$channel_message_ID" , "$channel_thread_Id" ] } } }
This will create us a new field on the documents flowing through the pipeline telling us if there is a match on the 2 fields. We can then push this in to a $match stage
{ $match: { "idMatch" : true } }
Then you can run the rest of the $group:
{ "$group" : { "_id" : "$message_status", "count" : { "$sum" : 1 } } }
then sort stage:
{ "$sort" : { "_id" : 1 } }
So for example if we add the following documents to a mongodb collection:
db.test.insertMany([{
message_status: "In Progress",
channel_thread_Id: "A",
channel_message_ID: "A"
},
{
message_status: "Completed",
channel_thread_Id: "A",
channel_message_ID: "A"
},
{
message_status: "In Progress",
channel_thread_Id: "A",
channel_message_ID: "B"
},
{
message_status: "Completed",
channel_thread_Id: "A",
channel_message_ID: "B"
}]);
{
"acknowledged" : true,
"insertedIds" : [
ObjectId("599abef4f0cd60f52d67215a"),
ObjectId("599abef4f0cd60f52d67215b"),
ObjectId("599abef4f0cd60f52d67215c"),
ObjectId("599abef4f0cd60f52d67215d")
]
}
We can then run the following aggregation query:
db.test.aggregate([
{ "$addFields" : { "idMatch" : { "$eq" : [ "$channel_message_ID" , "$channel_thread_Id" ] } } },
{ $match: { "idMatch" : true } },
{ "$group" : { "_id" : "$message_status", "count" : { "$sum" : 1 } } },
{ "$sort" : { "_id" : 1 } }
]);
Which will return the expected results of
{ "_id" : "Completed", "count" : 1 }
{ "_id" : "In Progress", "count" : 1 }