如何構建一個「group_by」SQL查詢在瓶頸不安？

我正在使用flask_sqlalchemy和flask_restless創建一個API端點來訪問PostgreSQL數據庫中的數據。我如何構建以下SQL查詢在瓶子裏不安？如何構建一個「group_by」SQL查詢在瓶頸不安？

SELECT AVG("SpeedBand"), "Location" 
FROM public.traffic_data 
WHERE "RoadName"='ABC ROAD' 
GROUP BY "Location"

這將返回屬於「ABC ROAD」的所有座標對和每對座標的平均時速：

avg | Location 
------------------------ 
1)'1.52' | 'X1 Y1 X2 Y2' 
2)'1.85' | 'X3 Y3 X4 Y4' 
------------------------

目前，這個查詢：

http://127.0.0.1:5000/api/traffic_data?q={"filters":[{"name":"RoadName","op":"==","val":"ABC ROAD"}]}

返回屬於「ABC ROAD」的所有數據的JSON字符串以及不同時間的所有速度數據：

{ 
    "num_results": 26, 
    "objects": [ 
    { 
     "DateTime": "2017-09-07T19:25:37.035325", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 3, 
     "id": 34094 
    }, 
    { 
     "DateTime": "2017-09-07T19:25:37.035325", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 1, 
     "id": 38003 
    }, 
    { 
     "DateTime": "2017-09-13T09:57:07.163900", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 1, 
     "id": 92874 
    }, 
    { 
     "DateTime": "2017-09-13T09:57:07.163900", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 1, 
     "id": 96783 
    }, 
    { 
     "DateTime": "2017-09-13T09:57:07.163900", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 1, 
     "id": 114755 
    }, 
    { 
     "DateTime": "2017-09-13T09:57:07.163900", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 114756 
    }, 
    { 
     "DateTime": "2017-09-13T10:08:17.727949", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 151654 
    }, 
    { 
     "DateTime": "2017-09-13T10:08:17.727949", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 155563 
    }, 
    { 
     "DateTime": "2017-09-13T10:19:39.040191", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 210434 
    }, 
    { 
     "DateTime": "2017-09-13T10:19:39.040191", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 214343 
    }, 
    { 
     "DateTime": "2017-09-13T10:27:51.307349", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 269214 
    }, 
    { 
     "DateTime": "2017-09-13T10:42:36.724985", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 327994 
    }, 
    { 
     "DateTime": "2017-09-13T10:42:36.724985", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 331903 
    }, 
    { 
     "DateTime": "2017-09-13T10:42:36.724985", 
     "LinkID": "109002906", 
     "Location": "X1 Y1 X2 Y2", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 1, 
     "id": 349875 
    }, 
    { 
     "DateTime": "2017-09-13T10:42:36.724985", 
     "LinkID": "109002907", 
     "Location": "X3 Y3 X4 Y4", 
     "RoadName": "ABC ROAD", 
     "SpeedBand": 2, 
     "id": 349876 
    }, 

    . . . 


    ], 
    "page": 1, 
    "total_pages": 1 
}

來源

2017-09-21 green_socks

您是否可以不定義自己的端點來準確運行該SQL？ –

我可以在SQLAlchemy中寫入相同的查詢結果= session.query（func.avg（TrafficData.SpeedBand），TrafficData.Location）.group_by（TrafficData.Location）.filter（TrafficData.RoadName =='ABC ROAD'） .all（）' 但我該如何將它寫入端點？ [鏈接]（https://flask-restless.readthedocs.io/en/stable/customizing.html） –

你可以寫入一個方法... https://flask-restless.readthedocs.io/en/ stable/customizing.html＃custom-queries –

對於組，您需要使用以下格式指定feild。 GROUP_BY 形式的對象的列表：

{"field": <fieldname>}

這裏字段名是用來按組由列。

來源

2017-09-21 02:17:57

你有一個這樣工作的例子嗎？我嘗試了以下'{「filters」：[{「name」：「RoadName」，「op」：「==」，「val」：「ABC ROAD」}]，「group_by」：[{「field 「：」Location「}]}'但是得到一個ProgrammingError響應。 –

如何構建一個「group_by」SQL查詢在瓶頸不安？

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