KSQL 事件合并 - 基于时间戳组合来自单个流的事件

Question

我正在尝试使用 ksql 将来自单个输入流的多个事件组合成一个按时间戳分组的单个输出事件。我还希望输出事件包含输入事件的平均值，尽管这不是严格意义上的 nessersay，而且更好。

输入流：温度

event1: {location: "hallway", value: 23, property_Id: "123", timestamp: "1551645625878"} 
event2: {location: "bedroom", value: 21, property_Id: "123", timestamp: "1551645625878"}
event3: {location: "kitchen", value: 20, property_Id: "123", timestamp: "1551645625878"}
event4: {location: "hallway", value: 19, property_Id: "123", timestamp: "9991645925878"} 
event5: {location: "bedroom", value: 18, property_Id: "123", timestamp: "9991645925878"}
event6: {location: "kitchen", value: 18, property_Id: "123", timestamp: "9991645925878"}

（所需）输出流：

event1:
{
    "property_id": "123",
    "timestamp": "1551645625878",
    "average_temperature": 21,   
    "temperature": [
        {
            "location": "hallway",
            "value": 23
        },
        {
            "location": "bedroom",
            "value": 21
        },
        {
            "location": "kitchen",
            "value": 20
        }
    ]
}

event2:
{
    "property_id": "123",
    "timestamp": "9991645925878",
    "average_temperature": 18,   
    "temperature": [
        {
            "location": "hallway",
            "value": 19
        },
        {
            "location": "bedroom",
            "value": 18
        },
        {
            "location": "kitchen",
            "value": 18
        }
    ]
}

据我所知，这使用 ksql 是不可能的，有人可以确认吗？

Answer 1

正确，您目前无法在 KSQL 中执行此操作。从 v5.1 / 2019 年 3 月开始，KSQL 可以读取但不能构建嵌套对象：https://github.com/confluentinc/ksql/issues/2147（如果需要，请点赞/评论）

您可以使用以下方法进行平均计算：

SELECT timestamp, SUM(value)/COUNT(*) AS avg_temp \
  FROM input_stream \
  GROUP BY timestamp;