CollectTop 返回的行比我在 Azure 流分析中预期的要多

Question

我上传了以下输入（在 Azure 门户中测试）：

[
  {"engineid":"engine001","eventtime":1,"tmp":19.3,"hum":0.22},
  {"engineid":"engine001","eventtime":2,"tmp":19.7,"hum":0.21},
  {"engineid":"engine002","eventtime":3,"tmp":20.4,"hum":0.25},
  {"engineid":"engine001","eventtime":4,"tmp":19.6,"hum":0.24}
]

然后我尝试获取记录组，这样我就有了每个引擎的最后两行。正如您在示例中看到的，我只有 2 个不同的引擎，所以我希望输出包含两条记录，每条记录都包含排名记录，但我得到 4 条输出记录。

这是我的查询：

-- Taking relevant fields from the input stream
WITH RelevantTelemetry AS
(
    SELECT  engineid, tmp, hum, eventtime
    FROM    [engine-telemetry] 
    WHERE   engineid IS NOT NULL
),
-- Grouping by engineid in TimeWindows
TimeWindows AS
(
    SELECT engineid, 
        CollectTop(2) OVER (ORDER BY eventtime DESC) as TimeWindow
    FROM
        [RelevantTelemetry]
    WHERE engineid IS NOT NULL
    GROUP BY SlidingWindow(hour, 24), engineid
)
--Output timewindows for verification purposes
SELECT TimeWindow
INTO debug
FROM TimeWindows

我使用了 TIMESTAMP BY 属性，更改了 GROUP BY 的顺序等，但我仍然有以下 4 条记录，而不是我期望的 2 条：

有什么想法吗？

[
{"TimeWindow":
  [
    {"rank":1,"value": "engineid":"engine001","tmp":0.0003,"hum":-0.0002,"eventtime":1}}
  ]},
{"TimeWindow":
  [
    {"rank":1,"value":{"engineid":"engine001","tmp":-0.0019,"hum":-0.0002,"eventtime":4}},
    {"rank":2,"value":{"engineid":"engine001","tmp":-0.0026,"hum":-0.0002,"eventtime":2}},
    {"rank":3,"value":{"engineid":"engine001","tmp":0.0003,"hum":-0.0002,"eventtime":1}}
  ]},
{"TimeWindow":
  [
    {"rank":1,"value":{"engineid":"engine002","tmp":0.0017,"hum":0.0003,"eventtime":3}}
  ]},
{"TimeWindow":
  [
    {"rank":1,"value":{"engineid":"engine001","tmp":-0.0019,"hum":-0.0002,"eventtime":4}},
    {"rank":2,"value":{"engineid":"engine001","tmp":-0.0026,"hum":-0.0002,"eventtime":2}}
  ]}
]

Answer 1

根据@SteveZhao 的建议，您需要使用 GROUP BY TumblingWindow(hour, 24), engineid 而不是 GROUP BY SlidingWindow(hour, 24), engineid

滑动window可以根据时间间隔重叠条目

更多信息请参考： https://docs.microsoft.com/en-us/azure/stream-analytics/stream-analytics-window-functions

CollectTop 返回的行比我在 Azure 流分析中预期的要多

CollectTop is returning more rows than I would expect in Azure Stream Analytics

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