Advanced MySQL knowledge points (7)

MySQL Advanced knowledge （ 7、 ... and ）

Intercept query analysis

1、 Slow log query

Concept

• MySQL The slow query log of is MySQL A type of logging provided , It is used to record in MySQL Statement with response time over threshold in , Specifically, the running time exceeds long_query_time It's worth it SQL, It will be recorded in the slow query log
• Specifically, the running time exceeds long_query_time It's worth it SQL, It will be recorded in the slow query log .long_query_time The default value is 10, It means running 10 Seconds or more
• It's up to him to see what SQL Beyond our maximum endurance time , Like one sql To perform more than 5 Second , We are slow SQL, I hope I can Collection over 5 Of a second sql, Before integration explain Conduct a comprehensive analysis

Use

By default ,MySQL Slow query log is not enabled in the database , We need to Manual To set this parameter

If it's not for tuning , It is generally not recommended to start this parameter , Because opening slow query log will bring some performance impact more or less . Slow query log supports writing log records to files

SQL sentence	describe	remarks
SHOW VARIABLES LIKE ‘%slow_query_log%’	Check whether the slow query log is on	By default slow_query_log The value of is OFF
set global slow_query_log=1	Open slow query log
SHOW VARIABLES LIKE ‘long_query_time%’	View slow query set threshold	Company ： second
set long_query_time=1	Set the slow query threshold	Company ： second

Long running queries sql, You can open the slow query log to view

2、 Batch data script

Create table statement

--dept  Departmental table 
CREATE TABLE `dept` (
`id` INT(11) NOT NULL AUTO_INCREMENT, `deptName` VARCHAR(30) DEFAULT NULL, `address` VARCHAR(40) DEFAULT NULL, ceo INT NULL , PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

-- emp  The employee table 
CREATE TABLE `emp` (
`id` INT(11) NOT NULL AUTO_INCREMENT, `empno` INT NOT NULL , `name` VARCHAR(20) DEFAULT NULL, `age` INT(3) DEFAULT NULL, `deptId` INT(11) DEFAULT NULL, PRIMARY KEY (`id`)
#CONSTRAINT `fk_dept_id` FOREIGN KEY (`deptId`) REFERENCES `t_dept` (`id`)
) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

Set parameters

Before executing the create function , First of all, please ensure log_bin_trust_function_creators Parameter is 1, namely on On state . Otherwise, an error will be reported

-- Inquire about 
SHOW VARIABLES LIKE 'log_bin_trust_function_creators';

-- Set up 
SET GLOBAL log_bin_trust_function_creators=1;

Write random functions

Randomly generate strings

--DELIMITER  It's used to change the end sign , Usually ends with a semicolon , But here is changed to  $$  ending 
DELIMITER $$
CREATE FUNCTION rand_string(n INT) RETURNS VARCHAR(255)
BEGIN
DECLARE chars_str VARCHAR(100) DEFAULT 'abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ';
DECLARE return_str VARCHAR(255) DEFAULT '';
DECLARE i INT DEFAULT 0;
WHILE i < n DO
SET return_str =CONCAT(return_str,SUBSTRING(chars_str,FLOOR(1+RAND()*52),1));
SET i = i + 1;
END WHILE;
RETURN return_str;
END $$

If you want to Delete function , execute ：

DROP FUNCTION rand_string;

Randomly generate department number

DELIMITER $$
CREATE FUNCTION rand_num (from_num INT ,to_num INT) RETURNS INT(11)
BEGIN
DECLARE i INT DEFAULT 0;
SET i = FLOOR(from_num +RAND()*(to_num -from_num+1)) ;
RETURN i;
END$$

If you want to Delete function , execute ：

drop function rand_num;

Create stored procedure

To create emp A stored procedure that inserts data into a table

DELIMITER $$
CREATE PROCEDURE insert_emp( START INT , max_num INT )
BEGIN
DECLARE i INT DEFAULT 0;
#set autocommit =0  hold  autocommit  Set to  0
SET autocommit = 0;
REPEAT
SET i = i + 1;
INSERT INTO emp (empno, NAME ,age ,deptid ) VALUES ((START+i) ,rand_string(6) , rand_num(30,50),rand_num(1,10000));
UNTIL i = max_num
END REPEAT;
COMMIT;
END$$

-- Delete 
-- DELIMITER ;
-- drop PROCEDURE insert_emp;

To create dept A stored procedure that inserts data into a table

-- Execute stored procedures , Go to  dept  Add random data to table 
DELIMITER $$
CREATE PROCEDURE `insert_dept`( max_num INT )
BEGIN
DECLARE i INT DEFAULT 0;
SET autocommit = 0;
REPEAT
SET i = i + 1;
INSERT INTO dept ( deptname,address,ceo ) VALUES (rand_string(8),rand_string(10),rand_num(1,500000));
UNTIL i = max_num
END REPEAT;
COMMIT;
END$$

-- Delete 
-- DELIMITER ;
-- drop PROCEDURE insert_dept;

Calling stored procedure

Add data to department table

-- Execute stored procedures , Go to  dept  Table to add  1  Ten thousand data 
DELIMITER ;
CALL insert_dept(10000);

Add data to employee table

-- Execute stored procedures , Go to  emp  Table to add  50  Ten thousand data 
DELIMITER ;
CALL insert_emp(100000,500000);

Batch delete all indexes on a table

Delete the stored procedure of the index

DELIMITER $$
CREATE PROCEDURE `proc_drop_index`(dbname VARCHAR(200),tablename VARCHAR(200))
BEGIN
DECLARE done INT DEFAULT 0;
DECLARE ct INT DEFAULT 0;
DECLARE _index VARCHAR(200) DEFAULT '';
DECLARE _cur CURSOR FOR SELECT index_name FROM information_schema.STATISTICS WHERE
table_schema=dbname AND table_name=tablename AND seq_in_index=1 AND index_name <>'PRIMARY' ;
DECLARE CONTINUE HANDLER FOR NOT FOUND set done=2 ;
OPEN _cur;
FETCH _cur INTO _index;
WHILE _index<>'' DO
SET @str = CONCAT("drop index ",_index," on ",tablename );
PREPARE sql_str FROM @str ;
EXECUTE sql_str;
DEALLOCATE PREPARE sql_str;
SET _index='';
FETCH _cur INTO _index;
END WHILE;
CLOSE _cur;
END$$

Execute stored procedures

CALL proc_drop_index("dbname","tablename");