KSQL 事件合并——基于时间戳合并来自单个流的事件

Question

我正在尝试使用 ksql 将单个输入流中的多个事件合并为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，虽然这不是严格意义上的 nessersay，但更好。

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"}

（期望）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，使用 ksql 是不可能的，任何人都可以确认吗？

Answer 1

正确，您目前无法在 KSQL 中执行此操作。自 v5.1/2019 年 3 月起，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 upvote/comment）

您可以通过以下方式进行平均计算：

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

KSQL 事件合并——基于时间戳合并来自单个流的事件

KSQL Event Merging - Combining events from a single stream based on timestamp

apache-kafka

ksqldb