MongoDB和C＃-检查文档是否存在，是否不插入

Question

I currently get a list of 50 restaurants from the Yelp Fusion API. I want to save these restaurants in my database for further use in my application.

Since I get this list based on the user's coordinates, it's possible the API will return restaurants that are already in my database. To prevent duplicates, I check if the restaurant ID provided by yelp already exists in the database. If it's already in my database, it won't insert that restaurant.

I'm using a MongoDB database.

I accomplish this using the following function:

public async static void CheckSubjects(List<Subject> subjects)
    {
        SubjectRepository rep = new SubjectRepository();
        List<Subject> insert = new List<Subject>();
        foreach (var item in subjects)
        {
            if (!rep.SubjectsExists(item).GetAwaiter().GetResult())
                insert.Add(item);
        }
        if (insert.Count > 0)
            await rep.CreateAllSubjects(insert);
    }

In this function a subject is a restaurant. The repository is the class which communicates with the database.

This is my function that checks if the restaurant already exists:

public async Task<bool> SubjectExists(Subject sub)
    {
        var result = await db.Subjects.Find(Builders<Subject>.Filter.Eq("yelp_id", sub.yelp_id)).FirstOrDefaultAsync();
        if (result != null)
            return true;
        else
            return false;
    }

You can see it's very performance heavy to make 50 calls to the database to see if it already exists. I did some research and found the upsert function from MongoDB. I just don't know how I could use this in my scenario.

Could anyone help me out with this? Thanks in advance!

Answer 1

When using upsert as an option during an update, if a document doesn't exist, it will be created. Instead of trying to find each restaurant ans then insert them, you could call an update for each of them with upsert set as true (I think it'd be something like this )

Another aproach that could be even more efficient would be setting yelp_id as a key by creating an unique index , then when inserting duplicated entries it would fail, so you wouldn't need to worry if it is already in the database.