MySQL优化一例

DELIMITER $$

USE `xxx`$$

DROP FUNCTION IF EXISTS `F_getBuluDates`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `F_getBuluDates`(`PuserId` INT(11)) RETURNS VARCHAR(3000) CHARSET gbk

BEGIN

DECLARE buluDate,buluDateTime,LiWaibuluDates,nowdate,bldate VARCHAR(3000) DEFAULT "";

DECLARE rtMsg,RuserName,maxRiZhiDate,btjrqs,blyqrq,tmpdate,yxblsj VARCHAR(255) DEFAULT "";

DECLARE Ra51count INT(30);

DECLARE RbeginDate,RendDate,RtmpDate VARCHAR(2550);

DECLARE u,gqcount,a21Count INT(30) DEFAULT 0;

DECLARE allReadRows,readRows,mySYL,blCount,recordCount,btjryCount,btjrqCount,yxblts,i INT(11) DEFAULT 0;

SELECT a5204,a5205 INTO yxblts,yxblsj FROM a52 WHERE a5218="xxxxxxx" LIMIT 0,1;    

SELECT username INTO RuserName FROM USER WHERE id=PuserId;

SELECT COUNT(id) INTO btjryCount FROM a52 WHERE a5214=PuserId AND a5218='xxxxx';

IF btjryCount=0 THEN    

SELECT GROUP_CONCAT(a5215) INTO btjrqs FROM a52 WHERE  a5218='btjrq';

SET tmpdate=CURDATE();

SET nowdate=DATE_SUB(CURDATE(),INTERVAL yxblts DAY);

REPEAT

SELECT MAX(a2104) INTO maxRiZhiDate FROM a21 WHERE issubmit='y' AND a2104<tmpdate AND FIND_IN_SET(a2104,bldate)=0;

SET tmpdate=maxRiZhiDate;

IF tmpdate>=nowdate THEN

	IF F_isWorkDay(maxRiZhiDate)=1 OR ISNULL(maxRiZhiDate) THEN

		IF NOT ISNULL(maxRiZhiDate) AND LENGTH(maxRiZhiDate)>0 THEN

			IF FIND_IN_SET(maxRiZhiDate,btjrqs)=0 THEN

				SELECT COUNT(id) INTO recordCount FROM a21 WHERE a2104=maxRiZhiDate AND creatorid=PuserId;

				IF recordCount=0 THEN

					IF DAYOFWEEK(maxRiZhiDate)=6 THEN

						SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+2+yxblts)," ",yxblsj);

					ELSEIF DAYOFWEEK(maxRiZhiDate)=7 THEN

						SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+1+yxblts)," ",yxblsj);

					ELSE

						SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+yxblts)," ",yxblsj);

					END IF;

					IF(CURRENT_TIMESTAMP()<buluDateTime) THEN

						SET buluDate=maxRiZhiDate;

					END IF;

				END IF;

			END IF;

		END IF;  

	END IF;

	IF CHAR_LENGTH(buluDate)>0 THEN

		IF CHAR_LENGTH(bldate)>0 THEN

			SET bldate=CONCAT(buluDate,",",bldate);

		ELSE

			SET bldate=buluDate;

		END IF;

	END IF;

END IF;

SET buluDate='';

UNTIL tmpdate<=nowdate

END REPEAT;

SELECT COUNT(id) INTO gqcount FROM a52 WHERE a5216=CURDATE() AND a5218='xxxxxx';

IF gqcount>0 THEN

SELECT a5215 INTO blyqrq FROM a52 WHERE a5216=CURDATE() AND a5218='xxxxxx';

SELECT COUNT(id) INTO a21Count FROM a21 WHERE a2104=blyqrq AND creatorid=PuserId;

IF a21Count=0 THEN

IF FIND_IN_SET(blyqrq,bldate)=0 THEN

IF CHAR_LENGTH(bldate)>0 THEN

SET bldate=CONCAT(blyqrq,",",bldate);

ELSE

SET bldate=blyqrq;

END IF;

END IF;

END IF;

END IF;

IF ISNULL(btjrqs) THEN

SET btjrqs="";

END IF;

SELECT GROUP_CONCAT(a5108) INTO LiWaibuluDates FROM a51 WHERE a5110='y' AND F_ifInSet(a5108,btjrqs)=0 AND a5106 LIKE RuserName AND a5112='否' AND CONCAT(a5108," ",a5113)<CURRENT_TIMESTAMP() AND CURRENT_TIMESTAMP()<CONCAT(a5114," ",a5113);

IF NOT ISNULL(LiWaibuluDates) AND LENGTH(TRIM(LiWaibuluDates))>0 THEN

IF CHAR_LENGTH(bldate)>0 THEN

SET bldate=CONCAT(LiWaibuluDates,",",bldate);

ELSE

SET bldate=LiWaibuluDates;

END IF;

END IF;       

SELECT COUNT(id) INTO RA51count FROM a51 WHERE a5110='n' AND F_getid1value2(a5105,1)=PuserId;

IF RA51count>0 THEN

SET u=0;

WHILE u< RA51count DO

SELECT a5108,a5109 INTO RbeginDate,RendDate FROM a51 WHERE a5110='n' AND F_getid1value2(a5105,1)=PuserId ORDER BY id LIMIT u,1;

SET RtmpDate=RbeginDate;

WHILE RtmpDate<=RendDate DO

IF FIND_IN_SET(RtmpDate,bldate)>0 THEN

SET bldate=F_removeFromSet(RtmpDate,bldate);

END IF;

SET RtmpDate=DATE_ADD(RtmpDate, INTERVAL 1 DAY);

END WHILE;

SET u=u+1;

END WHILE;

END IF;

END IF;  

RETURN bldate;

END$$

DELIMITER ;

在老系统中该函数调用一次需要话20多秒到30秒左右。

拿到sql之后，首先要确定思路。不能着急这下手。

1. 首先查看各个表的数据量：

select count(*) from xxx;

发现只有 a21 的数据量达到了十几万，其他表数据量都比较小。所以重点是 a21表，仔细阅读了一遍函数的定义，发现涉及到 a21 的有一处循环：

REPEAT

SELECT MAX(a2104) INTO maxRiZhiDate FROM a21 WHERE issubmit='y' AND a2104<tmpdate AND FIND_IN_SET(a2104,bldate)=0;

很显然使用了 find_in_set 函数，所以改语句无法使用索引。所以想要简单的通过增加索引来解决问题，应该是行不通的。

这样就定位到了函数运行慢的问题。结合业务理解改函数的含义。

为了使用索引，我们需要去掉 find_in_set 函数，理解了业务和原函数的功能之后，对改函数的 repeat 循环部分进行了重写：

DELIMITER $$

USE `oa`$$

DROP FUNCTION IF EXISTS `F_getBuluDates_inner`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `F_getBuluDates_inner`(`PuserId` INT(11), tmpdate VARCHAR(32), nowdate VARCHAR(32)) RETURNS VARCHAR(3000) CHARSET gbk

BEGIN

DECLARE buluDate,buluDateTime,LiWaibuluDates,bldate VARCHAR(3000) DEFAULT "";

DECLARE rtMsg,RuserName,maxRiZhiDate,btjrqs,blyqrq,yxblsj VARCHAR(255) DEFAULT "";

DECLARE Ra51count INT(30);

DECLARE RbeginDate,RendDate,RtmpDate VARCHAR(2550);

DECLARE u,gqcount,a21Count INT(30) DEFAULT 0;

DECLARE allReadRows,readRows,mySYL,blCount,recordCount,btjryCount,btjrqCount,yxblts,i INT(11) DEFAULT 0;

DECLARE no_more_data INT DEFAULT 0;

DECLARE my_cursor CURSOR FOR SELECT DISTINCT a2104 FROM a21 WHERE issubmit='y' AND a2104 < tmpdate AND a2104 >= nowdate ORDER BY a2104 DESC;

DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_data = 1;

SELECT a5204,a5205 INTO yxblts,yxblsj FROM a52 WHERE a5218="gzrz" LIMIT 0,1;    

SELECT username INTO RuserName FROM USER WHERE id=PuserId;

SELECT COUNT(id) INTO btjryCount FROM a52 WHERE a5214=PuserId AND a5218='xxxxx';

IF btjryCount=0 THEN    

SELECT GROUP_CONCAT(a5215) INTO btjrqs FROM a52 WHERE  a5218='xxx';   

OPEN my_cursor;

FETCH my_cursor INTO maxRiZhiDate;

REPEAT

    IF F_isWorkDay(maxRiZhiDate)=1 OR ISNULL(maxRiZhiDate) THEN

        IF NOT ISNULL(maxRiZhiDate) AND LENGTH(maxRiZhiDate)>0 THEN

            IF FIND_IN_SET(maxRiZhiDate,btjrqs)=0 THEN

                SELECT COUNT(id) INTO recordCount FROM a21 WHERE a2104=maxRiZhiDate AND creatorid=PuserId;

                IF recordCount=0 THEN

                    IF DAYOFWEEK(maxRiZhiDate)=6 THEN

                        SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+2+yxblts)," ",yxblsj);

                    ELSEIF DAYOFWEEK(maxRiZhiDate)=7 THEN

                        SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+1+yxblts)," ",yxblsj);

                    ELSE

                        SET buluDateTime=CONCAT(FROM_DAYS(TO_DAYS(maxRiZhiDate)+yxblts)," ",yxblsj);

                    END IF;

                    IF(CURRENT_TIMESTAMP()<buluDateTime) THEN

                        SET buluDate=maxRiZhiDate;

                    END IF;

                END IF;

            END IF;

        END IF;  

    END IF;

    IF CHAR_LENGTH(buluDate)>0 THEN

        IF CHAR_LENGTH(bldate)>0 THEN

            SET bldate=CONCAT(buluDate,",",bldate);

        ELSE

            SET bldate=buluDate;

        END IF;

    END IF;

FETCH my_cursor INTO maxRiZhiDate;

SET buluDate='';

UNTIL no_more_data = 1

END REPEAT;

SELECT COUNT(id) INTO gqcount FROM a52 WHERE a5216=CURDATE() AND a5218='xxx';

IF gqcount>0 THEN

SELECT a5215 INTO blyqrq FROM a52 WHERE a5216=CURDATE() AND a5218='xxxxxxxxxx';

SELECT COUNT(id) INTO a21Count FROM a21 WHERE a2104=blyqrq AND creatorid=PuserId;

IF a21Count=0 THEN

IF FIND_IN_SET(blyqrq,bldate)=0 THEN

IF CHAR_LENGTH(bldate)>0 THEN

SET bldate=CONCAT(blyqrq,",",bldate);

ELSE

SET bldate=blyqrq;

END IF;

END IF;

END IF;

END IF;

IF ISNULL(btjrqs) THEN

SET btjrqs="";

END IF;

SELECT GROUP_CONCAT(a5108) INTO LiWaibuluDates FROM a51 WHERE a5110='y' AND F_ifInSet(a5108,btjrqs)=0 AND a5106 LIKE RuserName AND a5112='否' AND CONCAT(a5108," ",a5113)<CURRENT_TIMESTAMP() AND CURRENT_TIMESTAMP()<CONCAT(a5114," ",a5113);

IF NOT ISNULL(LiWaibuluDates) AND LENGTH(TRIM(LiWaibuluDates))>0 THEN

IF CHAR_LENGTH(bldate)>0 THEN

SET bldate=CONCAT(LiWaibuluDates,",",bldate);

ELSE

SET bldate=LiWaibuluDates;

END IF;

END IF;       

SELECT COUNT(id) INTO RA51count FROM a51 WHERE a5110='n' AND F_getid1value2(a5105,1)=PuserId;

IF RA51count>0 THEN

SET u=0;

WHILE u< RA51count DO

SELECT a5108,a5109 INTO RbeginDate,RendDate FROM a51 WHERE a5110='n' AND F_getid1value2(a5105,1)=PuserId ORDER BY id LIMIT u,1;

SET RtmpDate=RbeginDate;

WHILE RtmpDate<=RendDate DO

IF FIND_IN_SET(RtmpDate,bldate)>0 THEN

SET bldate=F_removeFromSet(RtmpDate,bldate);

END IF;

SET RtmpDate=DATE_ADD(RtmpDate, INTERVAL 1 DAY);

END WHILE;

SET u=u+1;

END WHILE;

END IF;      

END IF;  

RETURN bldate;

END$$

DELIMITER ;

然后为了让新的 sql 使用索引：

DECLARE my_cursor CURSOR FOR

SELECT DISTINCT a2104 FROM a21 WHERE issubmit='y' AND a2104 < tmpdate AND a2104 >= nowdate ORDER BY a2104 DESC;

新增了索引：

add index issubmit_a2104(issubmit,a2104);

最终的提供给外部的调用函数：

DELIMITER $$

CREATE FUNCTION F_getBuluDates_new(`PuserId` INT(11)) RETURNS VARCHAR(3000) CHARSET gbk

BEGIN

    DECLARE bldate VARCHAR(3000) DEFAULT "";

    DECLARE tmpdate,nowdate VARCHAR(32) DEFAULT "";

    DECLARE yxblts INT;

    SELECT a5204 INTO yxblts FROM a52 WHERE a5218="gzrz" LIMIT 0,1;

    SET tmpdate = CURDATE();

    SET nowdate = DATE_SUB(tmpdate,INTERVAL yxblts DAY);

    SET bldate = F_getBuluDates_inner(PuserId,tmpdate,nowdate);

    RETURN bldate;

END

$$

测试效果：

mysql> select F_getBuluDates_new(10687);

+---------------------------------------------------------------------------------------------------------------+

| F_getBuluDates_new(10687)                                                                                    |

+---------------------------------------------------------------------------------------------------------------+

| 2016-08-04,2016-08-05,2016-08-08,2016-08-09,2016-08-10,2016-08-11,2016-08-12,2016-08-15,2016-08-16,2016-08-17 |

+---------------------------------------------------------------------------------------------------------------+

1 row in set (1.10 sec)

mysql> select F_getBuluDates(10687);

+---------------------------------------------------------------------------------------------------------------+

| F_getBuluDates(10687)                                                                                         |

+---------------------------------------------------------------------------------------------------------------+

| 2016-08-04,2016-08-05,2016-08-08,2016-08-09,2016-08-10,2016-08-11,2016-08-12,2016-08-15,2016-08-16,2016-08-17 |

+---------------------------------------------------------------------------------------------------------------+

1 row in set (13.10 sec)

性能提升了 11 倍多。客户对效果很满意。

新的执行计划：

mysql> explain SELECT DISTINCT a2104 FROM a21 WHERE issubmit='y' AND a2104 < '2016-08-16' AND a2104 >= '2016-08-10' ORDER BY a2104 DESC;

+----+-------------+-------+-------+----------------------+----------------+---------+------+------+--------------------------+

| id | select_type | table | type  | possible_keys        | key            | key_len | ref  | rows | Extra                    |

+----+-------------+-------+-------+----------------------+----------------+---------+------+------+--------------------------+

|  1 | SIMPLE      | a21   | range | a2104,issubmit_a2104 | issubmit_a2104 | 516     | NULL |  834 | Using where; Using index |

+----+-------------+-------+-------+----------------------+----------------+---------+------+------+--------------------------+

1 row in set (0.00 sec)

总结：

从原函数实现来看，在数量小时，还是可以的。但是一旦数据量大了，就会出现性能问题。主要问题是在 where 条件中使用了太多的自定义函数，而且这个函数的参数还是表的数据列。
导致无法使用索引。无法使用索引就会进行全表扫描，所以数据量大时会导致性能问题。

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