使用 Mongo 驱动程序的 Azure Cosmos DB：获取计数而不获取基于 C#.Net 中子子文档中的元素的所有文档

Question

下面是我存储在 Azure MongoDB 中的 JSON 结构（粘贴了示例结构），我想使用 Plyrs 中存在的 userID 元素进行查询（ Sub Sub 文档）获取用户参加过的所有锦标赛的列表。

1. 我已尝试使用 Aggregate() 但未成功。请纠正我 如果我遗漏了一些东西，下面是它的代码。

2. 尝试使用构建器但未成功，使用构建器我最多可以检索一个级别（子集合，json（粘贴在下面）引用到 tbls ）在那里我可以在 Plyrs（子子集合）上查询的任何方式。

3. Azure MongoDB 是否支持 Aggregate() 或计数而不获取整个文档？

请指导我聚合

   var count = sampleMongoDataBase.GetCollection<GameInfo>(sampleCollectionName).Aggregate()
                    .Unwind<GameInfo, TableDocumet>(t => t.Tables)
                    .Unwind<TableDocumet, PlayerDocument>(p => p.Players)
                   .Match(x => x.UserID == "3fd30fa8-f5c5-4311-8741-4032142bbb33")
                   .Group(new MongoDB.Bson.BsonDocument { { "id", "$Plyrs._id" }, { "count", new MongoDB.Bson.BsonDocument("$sum", 1) } }); 

建设者

 mongoDataBase.GetCollection<GameInfo>(mongoCollectionName).Find(Builders<GameInfo>.Filter.ElemMatch(x => x.Tables,t => t.TableId == 1)).Count();

错误： 命令聚合失败：不支持“$group”。

JSON：

`

{
"TnId": 651,
"QnId": "7a5de5dc-b02f-4013-9d02-ebf8430e7a56",
"samt": 10,
"tbls": [
  {
    "TblId": 1,
    "Plyrs": [
      {
        "_id": 1048995,
        "UserId": "FC381A6D717B6973-711BD743AE90E6D7",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Roman Yates",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1048996,
        "UserId": "fc3e0971-2c3c-e697-b68a-33b12a207bc2",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Neil Gaines",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1048997,
        "UserId": "FC369812-6DC04066-A133-1C10EEBA1546",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Lori Reyes",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1048998,
        "UserId": "FC2AC461-C7FAD800D3D79A2CD2680C72",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Duane Hoffman",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1048999,
        "UserId": "FC39AFCF-688C-B61A-A0DB-80EADAC832CD",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Alfredo Ware",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049000,
        "UserId": "FC2B863D-9ACC-13C706EA-8E31917566DB",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Abigail Riddle",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      }
    ]
  },
  {
    "TblId": 2,
    "Plyrs": [
      {
        "_id": 1049001,
        "UserId": "FC2BCC93-DDAE-4622-8D1226BDF1181D63",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Rene Spence",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049002,
        "UserId": "FC3D0CF42017-C3BFF460-E8DBDE3D1D77",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "TU006918",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049003,
        "UserId": "FC2CDE495F34E557-77C8-4B10981B7758",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Marshall Lutz",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049004,
        "UserId": "FC3EE1FDB4913FF345AE90CD14BE3607",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Roberto Burton",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049005,
        "UserId": "FC378E3C-C2A0528F094A-7FB31BD9D278",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Summer Stephenson",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      },
      {
        "_id": 1049006,
        "UserId": "FC431BBB-A79D45A0EAB034676C755E5A",
        "St": 3,
        "PCS": 2,
        "ConnId": null,
        "DN": "Terence Fischer",
        "RB": 2,
        "LL": 1,
        "Chips": 5000,
        "Rank": 46,
        "ExitLvl": 0,
        "TRA": 0,
        "PRI": "",
        "IsAns": false
      }
    ]
  }

输出： 例如，计数：5

Answer 1

并非所有 MongoDB 查询功能都在 Cosmos MongoDB API 中出现，目前聚合管道是未实现的功能之一。这就是为什么您会收到错误消息，指出不支持 $group。

编辑 - 截至 2017 年 11 月，聚合管道现在是 Cosmos DB 的 MongoDB API 支持的操作。支持的功能的完整列表是here。

一般聚合 (sum, min, max, avg, count) 不久前被添​​加到 DocumentDB API。

目前，您必须在 MongoDB API 中进行自己的聚合。

注意：支持count()，因此假设您过滤数据（没有聚合管道），您可以执行以下操作：

db.collection.find({...}).count()

同样，您可以通过排序执行$min 或$max。所以对于$max，你可以这样来求foo的最大值：

db.collection.find({...},{foo:1}).sort({foo:-1}).limit(1)

Answer 2

对 Cosmos DB 的聚合管道支持处于私人预览阶段。请随时与团队或我联系，为您的数据库启用它。