與上加入（速度問題）的範圍

Question

我試圖運行下面的查詢的MySQL查詢：

SELECT formatted_journeys.*, MAX(speed) 
FROM formatted_journeys 
JOIN tracker.g_log 
    ON imeiid = vehicle 
    AND g_logid BETWEEN start_g_log AND end_g_log 
GROUP BY id 

然而，這似乎是極其緩慢。這是該查詢的解釋。

+----+-------------+--------------------+------+-------------------------------+-------+---------+-----------------------------------+------+----------+---------------------------------+ 
| id | select_type | table    | type | possible_keys     | key | key_len | ref        | rows | filtered | Extra       | 
+----+-------------+--------------------+------+-------------------------------+-------+---------+-----------------------------------+------+----------+---------------------------------+ 
| 1 | SIMPLE  | formatted_journeys | ALL | vehicle,start_g_log,end_g_log | NULL | NULL | NULL        | 824 | 100.00 | Using temporary; Using filesort | 
| 1 | SIMPLE  | g_log    | ref | PRIMARY,Dupes     | Dupes | 4  | motrak.formatted_journeys.vehicle | 1985 | 100.00 | Using where      | 
+----+-------------+--------------------+------+-------------------------------+-------+---------+-----------------------------------+------+----------+---------------------------------+ 
2 rows in set, 1 warning (0.02 sec) 

的表格如下所示：

formatted_journeys：

+-----------------+------------------+------+-----+---------+----------------+ 
| Field   | Type    | Null | Key | Default | Extra   | 
+-----------------+------------------+------+-----+---------+----------------+ 
| id    | int(11) unsigned | NO | PRI | NULL | auto_increment | 
| start_g_log  | int(11)   | YES | MUL | NULL |    | 
| end_g_log  | int(11)   | YES | MUL | NULL |    | 
| start_latitude | decimal(18,12) | YES |  | NULL |    | 
| start_longitude | decimal(18,12) | YES |  | NULL |    | 
| end_latitude | decimal(18,12) | YES |  | NULL |    | 
| end_longitude | decimal(18,12) | YES |  | NULL |    | 
| start_location | text    | YES |  | NULL |    | 
| end_location | text    | YES |  | NULL |    | 
| distance  | decimal(10,5) | YES |  | NULL |    | 
| start_date  | datetime   | YES |  | NULL |    | 
| end_date  | datetime   | YES |  | NULL |    | 
| vehicle   | int(11)   | YES | MUL | NULL |    | 
| private   | bit(1)   | NO |  | b'0' |    | 
+-----------------+------------------+------+-----+---------+----------------+ 

指數：

+--------------------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| Table    | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | 
+--------------------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| formatted_journeys |   0 | PRIMARY  |   1 | id   | A   |   830 |  NULL | NULL |  | BTREE  |   | 
| formatted_journeys |   1 | vehicle  |   1 | vehicle  | A   |   4 |  NULL | NULL | YES | BTREE  |   | 
| formatted_journeys |   1 | start_g_log |   1 | start_g_log | A   |   830 |  NULL | NULL | YES | BTREE  |   | 
| formatted_journeys |   1 | end_g_log |   1 | end_g_log | A   |   830 |  NULL | NULL | YES | BTREE  |   | 
+--------------------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 

tracker.g_log：

+-----------+------------------+------+-----+---------+----------------+ 
| Field  | Type    | Null | Key | Default | Extra   | 
+-----------+------------------+------+-----+---------+----------------+ 
| g_logid | int(10) unsigned | NO | PRI | NULL | auto_increment | 
| imeiid | int(10) unsigned | NO | MUL | NULL |    | 
| latitude | decimal(18,12) | YES |  | NULL |    | 
| longitude | decimal(18,12) | YES |  | NULL |    | 
| speed  | int(4)   | YES | MUL | NULL |    | 
| bearing | int(4)   | YES |  | NULL |    | 
| distance | decimal(10,5) | YES |  | NULL |    | 
| eventcode | int(10)   | YES |  | NULL |    | 
| status | int(10)   | YES |  | NULL |    | 
| date  | datetime   | YES |  | NULL |    | 
+-----------+------------------+------+-----+---------+----------------+ 

個

指數：

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | 
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| g_log |   0 | PRIMARY |   1 | g_logid  | A   |  31760 |  NULL | NULL |  | BTREE  |   | 
| g_log |   0 | Dupes |   1 | imeiid  | A   |   16 |  NULL | NULL |  | BTREE  |   | 
| g_log |   0 | Dupes |   2 | date  | A   |  31760 |  NULL | NULL | YES | BTREE  |   | 
| g_log |   0 | Dupes |   3 | eventcode | A   |  31760 |  NULL | NULL | YES | BTREE  |   | 
| g_log |   1 | speed |   1 | speed  | A   |   423 |  NULL | NULL | YES | BTREE  |   | 
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 

現在我知道，文件排序是不是一件好事，但我將如何擺脫它？

Answer 1

您幾乎不會擺脫Using temporary; Using filesort，但查詢可能會更快。

首先，嘗試重寫查詢爲：

SELECT * 
FROM (
    SELECT id, MAX(speed) as max_speed 
    FROM formatted_journeys 
    JOIN tracker.g_log 
    ON imeiid = vehicle 
     AND g_logid BETWEEN start_g_log AND end_g_log 
    GROUP BY id) as maxspeeds 
JOIN formatted_journeys USING (id); 

然後，您可以嘗試強制查詢使用覆蓋指數，儘管這是不容易的查詢。

首先嚐試：添加複合索引(vehicle, start_g_log, end_g_log)，並期待在解釋它是否被使用（你應該看到「使用索引」那裏）