如何使用TTL創建MongoDB集合？

我創建了一個物件集合

public class User
{
public User(string fullname, string email)
{
Fullname = fullname;
Email = email;
}

    public string Fullname { get; }
    public string Email { get; }
}

并創建索引和一些檔案

var collection = _database.GetCollection(“bar”);
collection.Indexes.CreateOne(new CreateIndexModel
(new BsonDocument(“lastModifiedDate”, 1), new CreateIndexOptions { ExpireAfter = new TimeSpan(0, 0, 30) }));

            var user = new User("Vasya", "[email protected]");
            collection.InsertOne(user.ToBsonDocument());
            var user1 = new User("Petya", "[email protected]");
            collection.InsertOne(user1.ToBsonDocument());
            var user2 = new User("Kolya", "[email protected]");
            collection.InsertOne(user2.ToBsonDocument());
            count = collection.CountDocuments(new BsonDocument());

但是當我看到 http://localhost:8081/db/dbtest/ 時，我看不到任何 TTL 并且檔案不會在 30 秒后過期。

我做錯了什么？如何使用 TTL 在其中創建集合或檔案？

uj5u.com熱心網友回復：

您的用戶物件沒有您在索引中指定的欄位

public class User
{
    public User(string fullname, string email, DateTime lastModifiedDate) 
    {
        Fullname = fullname;
        Email = email;
        LastModifiedDate = lastModifiedDate;
    }

    public string Fullname { get; }
    public string Email { get; }
    public DateTime LastModifiedDate { get; }
}

此外，MongoDB C# 驅動程式中序列化的默認約定不是駝峰式大小寫，因此您需要將索引更新為以下內容：

var collection = _database.GetCollection("bar");
collection.Indexes.CreateOne(new CreateIndexModel
(new BsonDocument("LastModifiedDate", 1), new CreateIndexOptions { ExpireAfter = new TimeSpan(0, 0, 30) }));

您可能還想通過使用您的 User 型別而不是 BsonDocument 來擁抱 C# 和 MongoDB 驅動程式為您提供的型別安全性。下面是如何執行此操作的示例。

using MongoDB.Driver;

var client = new MongoClient();
var database = client.GetDatabase("test");
var collection = database.GetCollection<User>("users");
await collection.Indexes.CreateOneAsync(
    Builders<User>.IndexKeys.Ascending(x => x.LastModifiedDate),
    new CreateIndexOptions { ExpireAfter = new TimeSpan(0, 0, 30) });

var user = new User("Vasya", "[email protected]", DateTime.UtcNow);
collection.InsertOne(user);
var user1 = new User("Petya", "[email protected]", DateTime.UtcNow);
collection.InsertOne(user1);
var user2 = new User("Kolya", "[email protected]", DateTime.UtcNow);
collection.InsertOne(user2);

for (var i = 0; i < 10; i  )
{
    var count = await collection.CountDocumentsAsync(Builders<User>.Filter.Empty);
    Console.WriteLine($"Count: {count} @ {DateTime.UtcNow}");
    await Task.Delay(10000);
}


// Count: 4 @ 02/01/2022 11:42:13
// Count: 4 @ 02/01/2022 11:42:23
// Count: 4 @ 02/01/2022 11:42:33
// Count: 4 @ 02/01/2022 11:42:43
// Count: 4 @ 02/01/2022 11:42:53
// Count: 1 @ 02/01/2022 11:43:03
// Count: 1 @ 02/01/2022 11:43:13
// Count: 1 @ 02/01/2022 11:43:23
// Count: 1 @ 02/01/2022 11:43:33
// Count: 0 @ 02/01/2022 11:43:43


public class User
{
    public User(string fullname, string email, DateTime lastModifiedDate)
    {
        Fullname = fullname;
        Email = email;
        LastModifiedDate = lastModifiedDate;
    }

    public string Fullname { get; }
    public string Email { get; }
    public DateTime LastModifiedDate { get; }
}

您可能會注意到檔案不會立即被洗掉，但如 MongoDB 檔案中所述

洗掉過期檔案的后臺任務每 60 秒運行一次。因此，在檔案到期和后臺任務運行之間的時間段內，檔案可能會保留在集合中。 https://docs.mongodb.com/manual/core/index-ttl/#timing-of-the-delete-operation

標籤：C＃ MongoDB mongodb-.net-驱动程序

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