C# MongoDB driver calculating data size is wrong

Working with Data
1

I am using MongoDB C# driver “2.13.0” with MongoDB.Bson version “2.13.0” to connect and insert and retrieve data from MongoDB.

Now as per official website the document limit is 16 MB https://www.mongodb.com/docs/manual/reference/limits/

But when I am trying to insert data which is in KB’s if I put it in Notepad but the code is complaining the size limit.

System.FormatException: Size 16948171 is larger than MaxDocumentSize 16793600

But when I am using file to insert from MongoDB shell using command it’s working fine. Means it’s not complaining for the size there. Written first delete and then insert query.

2

Thanks for reporting this. I attempted to reproduce it but was unable to. According to my attempt the calculation is spot on.

This is the test I wrote:

[Fact]
public void InsertOne_with_largest_possible_document_should_work()
{
    var collection = CreateCollection(); // returns IMongoCollection<C>

    var documentWithEmptyString = new C { Id = 1, S = "" };
    var documentOverhead = documentWithEmptyString.ToBson().Length; // equals 22 bytes

    var maxDocumentSize = 16777216; // 16 MB
    var maxStringSize = maxDocumentSize - documentOverhead; // equals 16777194 chars
    var largestPossibleDocument = new C { Id = 1, S = new string('x', maxStringSize) };
    largestPossibleDocument.ToBson().Length.Should().Be(maxDocumentSize);

    collection.InsertOne(largestPossibleDocument);
    var roundTrippedDocument = collection.FindSync("{}").Single();
    roundTrippedDocument.ToBson().Length.Should().Be(maxDocumentSize);

    var documentSizeOnServer = collection
        .Aggregate()
        .AppendStage<BsonDocument>("{ $project : { documentSize : { $bsonSize : '$$ROOT' }, _id : 0 } }")
        .Single();
    documentSizeOnServer["documentSize"].AsInt32.Should().Be(maxDocumentSize);
}

This is the class definition of C:

private class C
{
    public int Id { get; set; }
    public string S { get; set; }
}
3

I did just notice that in your error message the MaxDocumentSize is 16793600, whereas I was expecting 16777216.

So perhaps my test to reproduce does not match what you are doing.

Can you provide more information? Ideally you could provide us with a small standalone program that minimally reproduces the problem.