Cleaning up orphaned chunks in GridFS

Program.cs

using MongoDB.Bson;
using MongoDB.Driver;
using Serilog;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace Mongo
{
    internal class Program
    {
        private static async Task<int> Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
             .MinimumLevel.Debug()
             .WriteTo.Console()
             .WriteTo.File("mongo.txt")
             .CreateLogger();

            var mongoSettings = MongoClientSettings.FromConnectionString("");
            var mongoClient = new MongoClient(mongoSettings);
            var mongoDatabase = mongoClient.GetDatabase("packagesDb");
            var chunksCollection = mongoDatabase.GetCollection<BsonDocument>("packages.chunks");
            var filesCollection = mongoDatabase.GetCollection<BsonDocument>("packages.files");

            using var cts = new CancellationTokenSource();
            Console.CancelKeyPress += (sender, e) =>
            {
                e.Cancel = true;
                cts.Cancel();
            };

            var sw = new Stopwatch();
            var numberOfChunksDeleted = 0UL;

            try
            {
                var chunkFilter = Builders<BsonDocument>.Filter.Empty;
                
                using var cursor = await chunksCollection.FindAsync(chunkFilter, new FindOptions<BsonDocument, BsonDocument>()
                {
                    BatchSize = 1000,
                    Skip = 0,
                    Limit = 100_000,
                    //Sort = Builders<BsonDocument>.Sort.Descending("_id"),
                    Projection = Builders<BsonDocument>.Projection.Exclude("data")
                }, cts.Token);

                sw.Start();

                var uniqueFiles = new HashSet<string>();
                while (await cursor.MoveNextAsync(cts.Token))
                {
                    var batch = cursor.Current;

                    foreach (var gridFSChunk in batch)
                    {
                        var objecdId = gridFSChunk.GetValue("_id").AsObjectId;
                        uniqueFiles.Add(gridFSChunk.GetValue("files_id").AsObjectId.ToString());
                    }
                }
                
                foreach (var files_id in uniqueFiles)
                {
                    var filter = Builders<BsonDocument>.Filter.Eq("_id", new ObjectId(files_id));
                    var count = await filesCollection.CountDocumentsAsync(filter, null, cts.Token);
                    if (count > 0)
                    {
                        continue;
                    }

                    var deleteFilter = Builders<BsonDocument>.Filter.Eq("files_id", new ObjectId(files_id));
                    var deleteResult = await chunksCollection.DeleteManyAsync(deleteFilter, null,cts.Token);
                    numberOfChunksDeleted += (ulong)deleteResult.DeletedCount;
                    Log.Information("{0},{1}", deleteResult, files_id);
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "Something went wrong.");
            }
            finally
            {
                sw.Stop();
                Log.Information("Number of chunks deleted: {0}.", numberOfChunksDeleted);
                Log.Information("Elapsed time: {0} minutes.", sw.Elapsed.TotalMinutes);
                Log.CloseAndFlush();
            }

            return 0;
        }
    }
}

See https://github.com/Dualog-students/GridFSCleaner