mongo C# 驱动程序上的 unwind/project 出现问题

Question

我正在尝试从报告中获取所有点的数组，以便可以映射它们。为此，我需要一个 unwind/projection，但我正在努力解决它。

结果格式如下..

"totalPoints": 200,
    "points": [
        {
            "itemId": "5e9592edb4959a52b8493f6d",
            "itemName": "Numquam hic minus repellat sequi.",
            "name": null,
            "longitude": null,
            "latitude": null
        },
...

如您所见，我得到了底部 3 项的空值。

这是我正在使用的查询

            var points = await _reportDocs.Aggregate()
                .Match(filter.GenerateFilter())
                .Unwind<IntelReport, IntelReportLocationUnwound>(x => x.Locations)
                .Project(x => new LocationDto
                {
                    ItemId = x.Id,
                    ItemName = x.Name,
                    Name = x.Location.Name,
                    Latitude = x.Location.Point.Coordinates[1],
                    Longitude = x.Location.Point.Coordinates[0]
                })
                .ToListAsync();

这是原始报告class（但我删除了一些此处不需要的内容）

 public class IntelReport
    {
        [BsonId]
        [BsonRepresentation(BsonType.ObjectId)]
        public string Id { get; set; }
        public string ReportTitle { get; set; }
        public ICollection<Location> Locations { get; set; }

    }

和 classes 我认为我需要放松...

 public class LocationDto
    {
        [BsonRepresentation(BsonType.ObjectId)]
        public string ItemId { get; set; }
        public string ItemName { get; set; }
        public string Name { get; set; }
        public double? Longitude { get; set; }
        public double? Latitude { get; set; }
    }

    [BsonIgnoreExtraElements]
    public class IntelReportLocationUnwound
    {
        [BsonId]
        [BsonRepresentation(BsonType.ObjectId)]
        public string Id { get; set; }

        [BsonElement("ReportTitle")]
        [BsonIgnoreIfDefault]
        public string Name { get; set; }

        [BsonElement("locations")]
        [BsonIgnoreIfDefault]
        public LocationForAgg Location { get; set; }
    }

    public class LocationForAgg
    {
        [BsonElement("name")]
        [BsonIgnoreIfDefault]
        public string Name { get; set; }

        [BsonElement("point")]
        [BsonIgnoreIfDefault]
        public PointForAgg Point { get; set; }
    }

    public class PointForAgg
    {
        [BsonElement("coordinates")]
        [BsonIgnoreIfDefault]
        public double[] Coordinates { get; set; }
    }

Answer 1

$unwind 将子文档数组转换为单个子文档，因此 .Unwind<IntelReport, IntelReportLocationUnwound>(x => x.Locations) 之后的数据将如下所示：

{ 
    "_id" : ObjectId("5e968bd5cc41498362cee2d2"), 
    "ReportTitle" : "aa", 
    "Locations" : { 
        "ItemId" : ObjectId("5e968bd5cc41498362cee2d3"), 
        "ItemName" : "Name", 
        "Name" : "N", 
        "Longitude" : 15, 
        "Latitude" : -24 
    } 
}

这意味着您必须重新考虑 IntelReportLocationUnwound class 定义。您可以使用与 IntelReport 中相同的类型，因为 MongoDB 只会将其从数组转换为嵌套对象：

public class IntelReportLocationUnwound
{
    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }

    [BsonElement("ReportTitle")]
    [BsonIgnoreIfDefault]
    public string Name { get; set; }

    [BsonElement("Locations")]
    [BsonIgnoreIfDefault]
    public Location Location { get; set; }
}

然后你可以修改你的聚合：

.Project(x => new LocationDto
        {
            ItemId = x.Id,
            ItemName = x.Name,
            Name = x.Location.Name,
            Latitude = x.Location.Latitude,
            Longitude = x.Location.Longitude
        })

mongo C# 驱动程序上的 unwind/project 出现问题

Trouble with an unwind/project on mongo C# driver

c#

mongodb

mongodb-.net-driver