如何使用 MongoDB 访问深层嵌套数组（ASP.NET Core 2.2）

Question

我正在使用 MongoDB 设计一个库存管理系统。我有以下数据库结构：

inventory
└─storage_slots
└─storage_locations
...etc...

每添加一个新的Slot，就会在storage_locations集合中添加一棵代表slot在层次结构中的位置的树来表示它的位置（根据location, room, section, shelf ).到目前为止，我已经成功地添加了一个新项目，其中 none 个位置字段已被使用：（插槽也被添加到 storage_slots 集合中）

{
"_id" : ObjectId("5c57169f0863d665c7f13d27"),
"CreatedUtc" : {
    "$date" : 1549211298017
},
"UpdatedUtc" : {
    "$date" : 1549211298017
},
"Description" : null,
"Address" : null,
"StorageRooms" : [
    {
        "_id" : ObjectId("5c57169f0863d665c7f13d28"),
        "CreatedUtc" : {
            "$date" : 1549211297719
        },
        "UpdatedUtc" : {
            "$date" : 1549211297719
        },
        "Description" : null,
        "StorageSections" : [
            {
                "_id" : ObjectId("5c57169f0863d665c7f13d29"),
                "CreatedUtc" : {
                    "$date" : 1549211297719
                },
                "UpdatedUtc" : {
                    "$date" : 1549211297719
                },
                "Description" : null,
                "StorageShelves" : [
                    {
                        "_id" : ObjectId("5c57169f0863d665c7f13d2a"),
                        "CreatedUtc" : {
                            "$date" : 1549211297719
                        },
                        "UpdatedUtc" : {
                            "$date" : 1549211297719
                        },
                        "Description" : null,
                        "StorageSlotIds" : [
                            ObjectId("5c57169f0863d665c7f13d26")
                        ]
                    }
                ]
            }
        ]
    }
]
}

明确地说，storage_locations 是上面的层次结构，而 storage_slots 只是插槽的集合。

但是，如果字段已经存在于层次结构中，则以下代码是运行：（我从 post中得到灵感）

var filter = Builders<StorageLocation>.Filter.And(
            Builders<StorageLocation>.Filter.Where(location => location.Id == id),
            Builders<StorageLocation>.Filter.Eq("StorageRooms.Id", roomId),
            Builders<StorageLocation>.Filter.Eq("StorageRooms.$.StorageSections.Id", sectionId),
            Builders<StorageLocation>.Filter.Eq("StorageRooms.$.StorageSections.$.StorageShelves.Id", shelfId));
        var update =
            Builders<StorageLocation>.Update.Push("StorageRooms.$.StorageSections.$.StorageShelves.$.StorageSlotIds",
                storageSlotIds);
        return await UpdateAsync(filter, update, cancellationToken);

此外，如果只定义了其中的一些，那么我会混合使用这两种方法，但我决定不在此处显示，因为它们基于相同的原则构建，不会对问题有所帮助。

问题

只要上面的代码是运行。我收到以下错误：

InvalidCastException: Unable to cast object of type 'MongoDB.Bson.ObjectId[]' to type 'MongoDB.Bson.ObjectId'.

MongoDB.Bson.Serialization.Serializers.SerializerBase<TValue>.MongoDB.Bson.Serialization.IBsonSerializer.Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value)

//annoying scrollbar

错误发生在这一行：

return await UpdateAsync(filter, update, cancellationToken);

方法是：

public Task<UpdateResult> UpdateAsync(FilterDefinition<T> filter, UpdateDefinition<T> updateDefinition,
        string database, string collection, CancellationToken cancellationToken)
    {
        return _mongoContext.MongoClient.GetDatabase(database).GetCollection<T>(collection)
            .UpdateOneAsync(filter, updateDefinition.Set(o => o.UpdatedUtc, DateTime.UtcNow),
                cancellationToken: cancellationToken);
    }

额外内容

这里有一些更相关的类问题：

public class StorageLocation : Dbo
{
    public string Description { get; set; }
    public Address Address { get; set; }
    public IEnumerable<StorageRoom> StorageRooms { get; set; }
}
public class StorageRoom : Dbo
{
    public string Description { get; set; }
    public IEnumerable<StorageSection> StorageSections { get; set; }
}
public class StorageSection : Dbo
{
    public string Description { get; set; }
    public IEnumerable<StorageShelf> StorageShelves { get; set; }
}
public class StorageShelf : Dbo
{
    public string Description { get; set; }
    public IEnumerable<ObjectId> StorageSlotIds { get; set; }
}
public class StorageSlot : Dbo
{
    public string Description { get; set; }

    public ObjectId LocationId { get; set; }
    public ObjectId RoomId { get; set; }
    public ObjectId SectionId { get; set; }
    public ObjectId ShelfId { get; set; }

    ...etc...
}

Answer 1

您收到此错误是因为 $ positional operator 只能使用一次，而在您的情况下有多层嵌套数组。来自文档：

The positional $ operator cannot be used for queries which traverse more than one array, such as queries that traverse arrays nested within other arrays, because the replacement for the $ placeholder is a single value

要解决此问题，您可以使用 filtered positional 运算符，该运算符在 MongoDB 3.6 中引入。它允许您在更新路径中指定多个占位符，然后您可以使用 arrayFilters 为这些占位符定义条件。

var filter = Builders<StorageLocation>.Filter.And(
   Builders<StorageLocation>.Filter.Where(location => location.Id == id),
   Builders<StorageLocation>.Filter.Eq("StorageRooms._id", roomId));

var arrayFilters = new List<ArrayFilterDefinition>();
ArrayFilterDefinition<BsonDocument> sectionFilter = new BsonDocument("section._id", new BsonDocument("$eq", sectionId));
ArrayFilterDefinition<BsonDocument> shelfFilter = new BsonDocument("shelf._id", new BsonDocument("$eq", shelfId));
arrayFilters.Add(sectionFilter);
arrayFilters.Add(shelfFilter);

var updateOptions = new UpdateOptions { ArrayFilters = arrayFilters };


var update =
    Builders<StorageLocation>.Update.Push("StorageRooms.$.StorageSections.$[section].StorageShelves.$[shelf].StorageSlotIds",
        storageSlotIds);

await Col.UpdateOneAsync(filter, update, updateOptions);

如何使用 MongoDB 访问深层嵌套数组（ASP.NET Core 2.2）

How to access deeply nested array with MongoDB (ASP.NET Core 2.2)

c#

asp.net

arrays

ienumerable

mongodb

问题

额外内容