Mongoose aggregate query $max in $match - node.js

Question

I am new to mongoose, I am facing a problem while trying to fetch some data using aggregate query.
One part of my auction schema is:
"_id" : ObjectId("56c58be1faaa402c0d4ae66f"),
"auction_name" : "Auction2",
"auction_start_datetime" : ISODate("2016-02-18T09:30:00.000Z"),
"auction_end_datetime" : ISODate("2016-02-22T09:00:00.000Z"),
"auction_status" : "active",
"auction_series" : "GA-06-C",
"auction_reserve_price" : 1000,
"auction_increment_amount" : 200,
"fancy_numbers" : [
{
"number_end_datetime" : ISODate("2016-02-22T09:00:00.000Z"),
"number_start_datetime" : ISODate("2016-02-18T09:30:00.000Z"),
"increment_amount" : 200,
"reserve_price" : 1000,
"number" : 5000,
"_id" : ObjectId("56c58da3faaa402c0d4ae739"),
"bid_users" : [
{
"user_id" : "56c416a599ad7c9c1611b90b",
"bid_amount" : 7200,
"bid_time" : ISODate("2016-02-18T11:58:53.025Z"),
"user_name" : "amit#mailinator.com",
"_id" : ObjectId("56c5aec4acebf3b4061a645e")
},
{
"user_id" : "56c172dc302a2c90179c7fd1",
"bid_amount" : 15400,
"bid_time" : ISODate("2016-02-19T10:38:43.506Z"),
"user_name" : "rbidder#mailinator.com",
"_id" : ObjectId("56c5afe0d2baef7020ede1b6")
},
{
"user_id" : "56c477afb27a7ed824c54427",
"bid_amount" : 2800,
"bid_time" : ISODate("2016-02-18T11:56:58.830Z"),
"user_name" : "bidder2#mailinator.com",
"_id" : ObjectId("56c5b18a78c3fb340a8c6d75")
},
{
"user_id" : "56c5b17378c3fb340a8c6d73",
"bid_amount" : 5600,
"bid_time" : ISODate("2016-02-18T11:58:34.616Z"),
"user_name" : "bidder3#mailinator.com",
"_id" : ObjectId("56c5b1d778c3fb340a8c6d78")
}
]
}
]
Here, fancy_number is an array under auction collection and bid_users is an array under each fancy_number.
I have the user_id, I want to query and get only the bid_user records in which he is the highest bidder.
For example:
There are 3 users bidded 200,300,400 respectively, I want to get the
record (i.e number and amount) only if this particular user bid is 400
(highest). where ill be passing the user_id
The aggregate query which I wrote is:
var ObjectID = require('mongodb').ObjectID;
tempId = new ObjectID(req.body.aId);
auctionModel.aggregate({$match: {'_id': tempId}},
{$unwind: '$fancy_numbers'},
{$unwind:"$fancy_numbers.bid_users"},
{$group: {'_id':"$fancy_numbers.number" , maxBid: { $max: '$fancy_numbers.bid_users.bid_amount'}}},
function(err, bidData){
if(err){
console.log('Error :' + err);
}
else if(bidData) {
console.log(bidData);
}
});
Somehow this query is not working, its only giving records of max bid and number. I want records only if he is the highest bidder.

Answer 1

If I catch you correctly, please try to do it through $sort, and $limit to retrieve the highest bidder as below
auctionModel.aggregate(.aggregate([
{$match: {'_id': '123'}},
{$unwind: '$fancy_numbers'},
{$unwind: '$fancy_numbers.bid_users'},
{$sort: {bid_amount: 1}},
{$limit: 1}]);