查詢優化 - 花費太長時間並停止服務器

我的查詢生成一些關於加速，上次和平均速度的報告。這是我的查詢：查詢優化 - 花費太長時間並停止服務器

Select 
    r1 . *, r2.name, r2.notes, r2.serial 
From 
    (SELECT 
     k.idgps_unit, 
      MIN(k.dt) AS DT_Start, 
      MIN(CASE 
       WHEN k.RowNumber = 1 THEN k.Lat 
      END) AS Latitude_Start, 
      MIN(CASE 
       WHEN k.RowNumber = 1 THEN k.Long 
      END) AS Longitude_Start, 
      MIN(CASE 
       WHEN k.RowNumber = 1 THEN k.Speed_kmh 
      END) AS Speed_Start, 
      MAX(k.dt) AS dt_end, 
      MIN(CASE 
       WHEN k.RowNumber = MaxRowNo THEN k.Lat 
      END) AS Latitude_End, 
      MIN(CASE 
       WHEN k.RowNumber = MaxRowNo THEN k.Long 
      END) AS Longitude_End, 
      MIN(CASE 
       WHEN k.RowNumber = MaxRowNo THEN k.Speed_kmh 
      END) AS Speed_End, 
      AVG(Speed_kmh) AS Average_Speed 
    FROM 
     (SELECT 
     gps_unit_location . *, 
      @i:=CASE 
       WHEN Speed_Kmh > 80 AND @b = 0 THEN @i + 1 
       ELSE @i 
      END AS IntervalID, 
      @r:=CASE 
       WHEN Speed_Kmh > 80 AND @b = 0 THEN 1 
       ELSE @r + 1 
      END AS RowNumber, 
      @b:=CASE 
       WHEN Speed_Kmh > 80 THEN 1 
       ELSE 0 
      END AS IntervalCheck 
    FROM 
     gps_unit_location, (SELECT @i:=0) i, (SELECT @r:=0) r, (SELECT @b:=0) b 
    ORDER BY dt , idgps_unit_location) k 
    INNER JOIN (SELECT 
     IntervalID, MAX(RowNumber) AS MaxRowNo 
    FROM 
     (SELECT 
     gps_unit_location . *, 
      @i:=CASE 
       WHEN Speed_Kmh > 80 AND @b = 0 THEN @i + 1 
       ELSE @i 
      END AS IntervalID, 
      @r:=CASE 
       WHEN Speed_Kmh > 80 AND @b = 0 THEN 1 
       ELSE @r + 1 
      END AS RowNumber, 
      @b:=CASE 
       WHEN Speed_Kmh > 80 THEN 1 
       ELSE 0 
      END AS IntervalCheck 
    FROM 
     gps_unit_location, (SELECT @i:=0) i, (SELECT @r:=0) r, (SELECT @b:=0) b 
    ORDER BY dt , idgps_unit_location) d 
    WHERE 
     IntervalCheck = 1 
    GROUP BY IntervalID) MaxInt ON MaxInt.IntervalID = k.IntervalID 
    WHERE 
     k.IntervalCheck = 1 
      and k.idgps_unit in (SELECT 
       idgps_unit 
      FROM 
       instafleet.gps_unit 
      where 
       id_customer = (select 
         idcustomer 
        from 
         user 
        where 
         iduser = 14)) 
    GROUP BY k.IntervalID , k.idgps_unit) r1 
     Inner join 
    gps_unit r2 ON r1.idgps_unit = r2.idgps_unit

目前，它需要3分鐘783723條記錄。我認爲適當的指標可能會有所幫助;雖然經過一些試驗和錯誤，但我無法弄清楚。如果你認爲你可以提供幫助，並需要一些額外的信息 - 我會很高興你提供給你。

解釋 Explain

結果 Result

來源

2013-03-12 Andrew

這是一個很長的查詢別人來優化您的免費重寫。你可以把它分解成更小的查詢來隔離問題嗎？ – 2013-03-12 17:17:31

Marcus，我認爲添加合適的索引可以解決它的性能問題..不需要重做它...我可能是錯的:) – Andrew 2013-03-12 17:20:39

您正在使用哪種GUI軟件？ – dynamic 2013-03-20 18:33:47

添加一個索引有助於在許多情況下，但你有一個子查詢加盟另一子查詢，在當前表沒有索引可以幫助你加快。您可以在這裏使用索引的唯一方法是創建臨時表。

正如Markus指出的那樣，您需要將您的查詢分解爲幾個較小的查詢，這些查詢將結果存儲在臨時表中。比你可以添加索引給他們，並希望加快你的查詢。將大問題分解爲幾個較小問題的另一個好處是，您可以更好地分析哪個部分是較慢的問題並修復問題。

您還使用了一次子查詢兩次，這對性能不利，因爲結果未被緩存。

這裏是你如何能做到這一點的例子：如果在嵌套查詢（S）的字節數超過了緩衝池的大小（檢查innodb_buffer_pool_size）查詢將採取

DROP TEMPORARY TABLE IF EXISTS tmp_k; 
CREATE TEMPORARY TABLE tmp_k 
    ENGINE=Memory 
SELECT 
    gps_unit_location.*, 
    @i:= IF(((Speed_Kmh > 80) AND (@b = 0)), @i + 1, @i) AS IntervalID, 
    @r:= IF(((Speed_Kmh > 80) AND (@b = 0)), 1, @r + 1) AS RowNumber, 
    @b:= IF((Speed_Kmh > 80), 1, 0) AS IntervalCheck 
FROM 
    gps_unit_location, 
    (SELECT @i:=0) i, 
    (SELECT @r:=0) r, 
    (SELECT @b:=0) b 
ORDER BY 
    dt, 
    idgps_unit_location; 

ALTER TABLE tmp_k ADD INDEX (IntervalID); 

DROP TEMPORARY TABLE IF EXISTS tmp_max; 
CREATE TEMPORARY TABLE tmp_max 
    ENGINE=Memory 
SELECT 
    IntervalID, 
    MAX(RowNumber) AS MaxRowNo 
FROM 
    temp_k 
WHERE 
    IntervalCheck = 1 
GROUP BY 
    IntervalID; 

ALTER TABLE tmp_max ADD INDEX (IntervalID); 

SELECT 
    k.idgps_unit, 
    MIN(k.dt) AS DT_Start, 
    MIN(IF(k.RowNumber = 1, k.Lat, NULL)) AS Latitude_Start, 
    MIN(IF(k.RowNumber = 1, k.Long, NULL)) AS Longitude_Start, 
    MIN(IF(k.RowNumber = 1, k.Speed_kmh, NULL) AS Speed_Start, 
    MAX(k.dt) AS DT_End, 
    MIN(IF(k.RowNumber = m.MaxRowNo, k.Lat, NULL)) AS Latitude_End 
    MIN(IF(k.RowNumber = m.MaxRowNo, k.Long, NULL)) AS Longitude_End 
    MIN(IF(k.RowNumber = m.MaxRowNo, k.Speed_kmh, NULL)) AS Speed_End, 
    AVG(Speed_kmh) AS Average_Speed, 
    gu.name, 
    gu.notes, 
    gu.serial 
FROM 
    tmp_k AS k 
    INNER JOIN tmp_max AS m 
     USING(IntervalID) 
    INNER JOIN gps_unit AS gu 
     USING(idgps_unit) 
    INNER JOIN user AS u 
    ON (gu.idcustomer = u.idcustomer) 
WHERE 
    (k.IntervalCheck = 1) 
    AND (u.iduser = 14) 
GROUP BY 
    k.IntervalID, 
    k.idgps_unit; 

DROP TEMPORARY TABLE tmp_k; 
DROP TEMPORARY TABLE tmp_max;

來源

2013-03-18 22:14:38