Question

你能帮助我正确使用2.0驱动程序“拉（删除）”。

我有一个这样的集合，我想删除第一个跟随者字段命名为fethiye的追随者。

files, _ := ioutil.ReadDir(my_dir)
    for _, f := range files {
        fmt.Println(f.Name())
    }

如何修复此查询？

{
  "_id": ObjectId("554e05dfc90d3d4dfcaa2aea"),
  "username": "bodrum",
  "followerList": [
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "fethiye",
      "avatar": "fethiye.png"
    },
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "izmir",
      "avatar": "izmir.png"
    }
  ]
}

感谢。

Answer 1

使用过滤器删除数组元素时，需要使用PullFilter构建器而不是Pull（与整个元素匹配）。

var collection = db.GetCollection<Person>("people");
var filter = new BsonDocument("username", "bodrum");
var update = Builders<Person>.Update.PullFilter("followerList",
    Builders<Follower>.Filter.Eq("follower", "fethiye"));
var result = collection.FindOneAndUpdateAsync(filter, update).Result;

或者更简洁一点，使用lambdas：

var update = Builders<Person>.Update.PullFilter(p => p.followerList,
                                                f => f.follower == "fethiye");
var result = collection
    .FindOneAndUpdateAsync(p => p.username == "bodrum", update).Result;

Answer 2

这是我用来删除嵌套数组对象的方法

-parentpath：followerList
-propertie：follower
值：fethiye.png

var filter = new BsonDocument("_id", ObjectId.Parse(id));

    var updateValues = Builders<object>.Update.PullFilter(parentPath,
        Builders<object>.Filter.Eq(propertie, value));
        DatabaseCollection.FindOneAndUpdate(filter, updateValues);

删除更深层嵌套数组对象的示例：
让我们删除名为Doe

的对象

-parentPath：followerList.0.testArray
-propertie：name
- 值：Doe

    {
  "_id": ObjectId("554e05dfc90d3d4dfcaa2aea"),
  "username": "bodrum",
  "followerList": [
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "fethiye",
      "testArray": [
{
"name":"John"
},
{
"name":"Doe"
},
{
"name":"Jason"
}
]
    },
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "izmir",
      "avatar": "izmir.png"
    }
  ]
}

Answer 3

我可以使用MongoDB.Entities提供一个简单得多的解决方案。 person和followers存储在自己的集合中，代表一对多关系。

using System.Linq;
using MongoDB.Entities;

namespace StackOverflow
{
    public class Person : Entity
    {
        public string Username { get; set; }
        public Many<Follower> FollowerList { get; set; }

        public Person() => this.InitOneToMany(() => FollowerList);
    }

    public class Follower : Entity
    {
        public string Name { get; set; }
        public string Avatar { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            new DB("followers");

            var person1 = new Person { Username = "bodrum"};
            person1.Save();

            var follower1 = new Follower { Name = "fethiye", Avatar= "fethiye.png" };
            follower1.Save();

            var follower2 = new Follower { Name = "izmir", Avatar = "izmir.png" };
            follower2.Save();

            person1.FollowerList.Add(follower1);
            person1.FollowerList.Add(follower2);

            var fathiye = person1.FollowerList.Collection()
                                              .Where(p => p.Name == "fethiye")
                                              .FirstOrDefault();

            person1.FollowerList.Remove(fathiye);
        }
    }
}

Answer 4

假设您有一个收藏名称“人”，您可以使用PullFilter从数组中删除记录

var filterBuilder = Builders<Person>.Filter.Eq(person => person.username, "bodrum");

var updateBuilder = Builders<Person>.Update.PullFilter(p => p.followerList,
                       Builders<Person>.Filter.Eq(per => per.follower, "fethiye"));

var updateResult = collection.UpdateOne(filterBuilder, updateBuilder);

Console.WriteLine(
            $"MatchedCount: {updateResult.MatchedCount}, ModifiedCount: {updateResult.ModifiedCount}");

如果我们还需要删除过滤后的文档中的值数组，可以用此行替换更新构建器

var updateBuilder = Builders<Person>.Update.PullFilter(p => p.followerList,
                   Builders<Person>.Filter.In(per => per.follower, new List<string> {"fethiye", "izmir"}));

还可以保存许多文档，可以将updateOne替换为updateMany

var updateResult = collection.UpdateMany(filterBuilder, updateBuilder);

MongoDB .Net驱动2.0拉（删除元素）

4 个答案: