Sort in mongoDB using a specific order - c

Question

I am currently looking to sort the sub document, Clients, in a particular order based on an array.
The mongoDB structure is
{
"_id" : "1033",
"Name" : "Test",
"Clients" : [
{
"Id" : 1033,
"Types" : [
{
"Class" : "C",
"Service" : null
},
{
"Class" : "B",
"Service" : null
}
]
},
{
"Id" : 156136,
"Types" : [
{
"Class" : "A",
"Service" : null
},
{
"Class" : "B",
"Service" : null
},
{
"Class" : "C",
"Service" : null
},
{
"Class" : "D",
"Service" : null
}
]
}
]
}
I need the above document displayed in the order based on a array like [B, A, D, C]
So that the output would be as below:
{
"_id" : "1033",
"Name" : "Test",
"Clients" : [
{
"Id" : 1033,
"Types" : [
{
"Class" : "B",
"Service" : null
},
{
"Class" : "C",
"Service" : null
}
]
},
{
"Id" : 156136,
"Types" : [
{
"Class" : "B",
"Service" : null
},
{
"Class" : "A",
"Service" : null
},
{
"Class" : "D",
"Service" : null
},
{
"Class" : "C",
"Service" : null
}
]
}
]
}
Could you please help me on how to achieve this?
I am currently using MongoDB Driver for .Net

Answer 1

Custom ordering is possible via aggregation as specified here.

Answer 2

I've solved my problem with custom sorting , using $addFields and $indexOfArray aggregations.
let imagine that my document has two fields: BouqetId, Name
[
{ "BouqetId" : 2, "Name" : "Name2"},
{ "BouqetId" : 16, "Name" : "Name16"},
{ "BouqetId" : 25, "Name" : "Name25"},
{ "BouqetId" : 15, "Name" : "Name15"},
{ "BouqetId" : 125, "Name" : "Name125"},
{ "BouqetId" : 258, "Name" : "Name258"},
{ "BouqetId" : 127, "Name" : "Name127"}
...
]
and I want to search for Bouqet with Ids [258,15,2,16] and get them with this order.
1/ I filter my collection using $in operator in $match aggregation to get the required documents: view step one in code.
2/ I add a field using $addFields aggregation named Order and assign to it the index of the BouqetId in the searched array using $indexOfArray aggregation.
3/ finally I sort them using the newly added Order field.
4/ I get my custom-ordered result. I can remove the order field but it is ok for now.
here and exmaple in Nodejs :
var db = client.db("MyDatabase");
var collection = db.collection("Bouqets");
var pipeline = [
{
"$match": {
"BouqetId": {
"$in": [
258,
15,
2,
16
]
}
}
},
{
"$addFields": {
"Order": {
"$indexOfArray": [
[
258,
15,
2,
16
],
"$BouqetId"
]
}
}
},
{
"$sort": {
"Order": 1.0
}
}
];
var cursor = collection.aggregate(pipeline);
Here my result :
[
{ "BouqetId" : 258, "Name" : "Name258" , "Order" : 0},
{ "BouqetId" : 15, "Name" : "Name15", "Order" : 1},
{ "BouqetId" : 2, "Name" : "Name2", "Order" : 2},
{ "BouqetId" : 16, "Name" : "Name16", "Order" : 3}
]
here the same example in c# :
IMongoClient client = new MongoClient("mongodb://host:port/");
IMongoDatabase database = client.GetDatabase("MyDatabase");
IMongoCollection<BsonDocument> collection = database.GetCollection<BsonDocument>("Bouqets");
var options = new AggregateOptions()
{
AllowDiskUse = false
};
// my array
var searchArray = new int[] {258, 15, 2, 16};
PipelineDefinition<BsonDocument, BsonDocument> pipeline = new BsonDocument[]
{
new BsonDocument("$match", new BsonDocument()
.Add("BouqetId", new BsonDocument()
.Add("$in", new BsonArray(searchArray)
)
)),
new BsonDocument("$addFields", new BsonDocument()
.Add("Order", new BsonDocument()
.Add("$indexOfArray", new BsonArray()
.Add(new BsonArray(searchArray)
)
.Add("$BouqetId")
)
)),
new BsonDocument("$sort", new BsonDocument()
.Add("Order", 1.0))
};
var result = collection.Aggregate(pipeline, options).ToList();

Answer 3

Custom ordering is not possible in MongoDB. You can either sort ascending or descending.