是否可以在ArangoDB中编写查询以汇总联接文档中的值？

Question

假设您拥有普通会员和高级会员的电影订阅服务。

这是由用户活动生成的数据示例，并作为文档存储在集合中：

[
    {
        "eventType": "sessionInfo",
        "userType": "premium",
        "sessionGroupID": 1
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "starwars",
        "sessionGroupID": 1,
        "elapsed": 200
    },
    {
        "eventType": "sessionInfo",
        "userType": "premium",
        "sessionGroupID": 2
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "xmen",
        "sessionGroupID": 2,
        "elapsed": 500
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 3
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "xmen",
        "sessionGroupID": 3,
        "elapsed": 10
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 4
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "xmen",
        "sessionGroupID": 4,
        "elapsed": 100
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 5
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "xmen",
        "sessionGroupID": 5,
        "elapsed": 5
    },
    {
        "eventType": "mediaPlay",
        "productSKU": "starwars",
        "sessionGroupID": 5,
        "elapsed": 25
    }
]

您可以看到有两个“ eventTypes”：

• “ sessionInfo”文档具有整个用户会话共有的信息

• “ mediaPlay”文档存储了观看电影的秒数。

（每个“ mediaPlay”事件都包含sessionGroupID，因此可以将其与该会话相关联。）

---

问题1：

给定总计数千万个文档，您将如何编写一个查询，该查询将按userType分组的每部电影的观看时间总计？

所需的查询结果：

premium users - total of "elapsed":
    xmen: 500
    starwars: 200

normal users - total of "elapsed":
    xmen: 115
    starwars: 25

---

问题2：

如果对于这样的查询，数据的结构不是最佳的，那么理想的结构是什么？

• 例如，将“ mediaPlay”事件嵌套在每个“ sessionInfo”文档中作为嵌套数组会更好吗？

像这样？

[
    {
        "eventType": "sessionInfo",
        "userType": "premium",
        "sessionGroupID": 1,
        "viewLog": [
            {
                "eventType": "mediaPlay",
                "productSKU": "starwars",
                "sessionGroupID": 1,
                "elapsed": 200
            }
        ]
    },
    {
        "eventType": "sessionInfo",
        "userType": "premium",
        "sessionGroupID": 2,
        "viewLog": [
            {
                "eventType": "mediaPlay",
                "productSKU": "xmen",
                "sessionGroupID": 2,
                "elapsed": 500
            }
        ]
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 3,
        "viewLog": [
            {
                "eventType": "mediaPlay",
                "productSKU": "xmen",
                "sessionGroupID": 3,
                "elapsed": 10
            }
        ]
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 4,
        "viewLog": [
            {
                "eventType": "mediaPlay",
                "productSKU": "xmen",
                "sessionGroupID": 4,
                "elapsed": 100
            }
        ]
    },
    {
        "eventType": "sessionInfo",
        "userType": "normal",
        "sessionGroupID": 5,
        "viewLog": [
            {
                "eventType": "mediaPlay",
                "productSKU": "xmen",
                "sessionGroupID": 5,
                "elapsed": 5
            },
            {
                "eventType": "mediaPlay",
                "productSKU": "starwars",
                "sessionGroupID": 5,
                "elapsed": 25
            }
        ]
    }
]

感谢您提供的所有指导和建议！

Answer 1

以下查询遍历该集合，并收集按userTypes分组的所有会话ID。 然后，它创建一个子查询，该子查询将遍历集合并收集所有电影以及经过的时间之和，其中eventType为“ mediaPlay”，并且所收集的会话包含sessionGroupID 。

@@coll是一个绑定参数 ，其中包括您的集合名称。

FOR doc IN @@coll
  FILTER doc.eventType == "sessionInfo"
  COLLECT userTypes = doc.userType INTO sessions = doc.sessionGroupID
  RETURN {
    "userTypes" : userTypes,
    "movies" : (
      FOR event IN @@coll
        FILTER event.sessionGroupID IN sessions
        FILTER event.eventType == "mediaPlay"
        COLLECT movie = event.productSKU INTO elapsed = event.elapsed
        RETURN { "movie" : movie, "elapsed" : SUM(elapsed) }
      )
  }

该查询的结果是：

[
  {
    "userTypes": "normal",
    "movies": [
      {
        "movie": "starwars",
        "elapsed": 25
      },
      {
        "movie": "xmen",
        "elapsed": 115
      }
    ]
  },
  {
    "userTypes": "premium",
    "movies": [
      {
        "movie": "starwars",
        "elapsed": 200
      },
      {
        "movie": "xmen",
        "elapsed": 500
      }
    ]
  }
]

关于第二个问题。 嵌套数组/对象不会优化此查询，但是您应该将数据分成两个集合。 每个eventType （例如，将集合命名为eventType sessionInfo和mediaPlay ）。 这减少了所需的过滤器语句的数量，更重要的是，它使您可以分别通过sessionInfos和mediaPlays查询，从而极大地提高了性能。

该查询将如下所示：

FOR doc IN sessionInfo
  COLLECT userTypes = doc.userType INTO sessions = doc.sessionGroupID
  RETURN {
    "userTypes" : userTypes,
    "movies" : (
      FOR event IN mediaPlay
        FILTER event.sessionGroupID IN sessions
        COLLECT movie = event.productSKU INTO elapsed = event.elapsed
        RETURN { "movie" : movie, "elapsed" : SUM(elapsed) }
      )
  }