MongoDB find does not follow collation rule - json

Question

I wanted to create an index on a membershipAccount collection, that had a collation rule set that would allow the find method to find a username while being case-insensitive.
[
2,
{
"username" : 1.0
},
"username_1",
"kollecto_prod.membershipAccounts",
{
"locale" : "da",
"caseLevel" : false,
"caseFirst" : "off",
"strength" : 1,
"numericOrdering" : false,
"alternate" : "non-ignorable",
"maxVariable" : "punct",
"normalization" : false,
"backwards" : false,
"version" : "57.1"
}
]
I have a user named - user#test.com in my membershipAccountscollection.
But this is my result of my find queries:
db.getCollection('membershipAccounts').find({username: "user#test.com"}) // 1 result - ok
db.getCollection('membershipAccounts').find({username: "USER#test.com"}) // 0 results - nope
db.getCollection('membershipAccounts').find({username: "USER#TEST.com"}) // 0 results - nope
db.getCollection('membershipAccounts').find({username: "USER#TEST.COM"}) // 0 results - nope
Is my collation incorect or have I misunterstood the concept?

Answer 1

You need to either set the desired collation in the query, or set the default collation on the collection. Creating an index with a collation does not make that collation the default one used in queries.
Per query:
MongoDB Enterprise ruby-driver-rs:PRIMARY> db.foo.insert({v:'test'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise ruby-driver-rs:PRIMARY> db.foo.find({v:'TEST'}).collation({locale:'en',caseLevel:false,strength:1})
{ "_id" : ObjectId("5ed8302ba6de3bc31c771682"), "v" : "test" }
Default collation:
MongoDB Enterprise ruby-driver-rs:PRIMARY> c={locale:'en',caseLevel:false,strength:1}
{ "locale" : "en", "caseLevel" : false, "strength" : 1 }
MongoDB Enterprise ruby-driver-rs:PRIMARY> db.createCollection('bar',{collation:c})
{
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1591226649, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1591226649, 1)
}
MongoDB Enterprise ruby-driver-rs:PRIMARY> db.bar.insert({v:'test'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise ruby-driver-rs:PRIMARY> db.bar.find({v:'TEST'})
{ "_id" : ObjectId("5ed8311fa6de3bc31c771683"), "v" : "test" }

Answer 2

So what I ended up doing instead was in my code as follows:
var account = DBHelper.membershipAccountCollection.Find(
x => x.Username.ToLower().Contains(username)
).FirstOrDefault();
var cu = DBHelper.customerUserCollection.AsQueryable().First(
x => x.Email.ToLower().Contains(model.UserName)
);
This works since I already had the collection object in my C# code, so I could that way utilize the power of C# instead. I realize this is not a general answer to the overall question, but it works in my case. If anyone has a more generalized answer to this question I am more than happy to accept this as an answer at a later date.