MySQL log classification: error log, binary log, query log, slow query log

MySQL Strong performance , It is one of the most widely used databases at present , With  MySQL For learning the prototype, it is also convenient to master other databases later , Now let's give you Give a comprehensive explanation MySQL8.0 New features , From zero foundation to high-level one-stop learning , Combined with actual cases, we can gain something ！

▼ MySQL8.0 introduction - Advanced learning notes ：（ Summary ）

• The first 1 speak ：SQL Overview and database system introduction
• The first 2 speak ：MySQL brief introduction 、 Detailed installation steps and use
• The first 3 speak ：MySQL Common graphics management tools
• The first 4 speak ：MySQL Basic operation of database -DDL 
• The first 5 speak ：MySQL Basic operation of database -DML
• The first 6 speak ：MySQL Classification of constraints 、 Function and usage
• The first 7 speak ：MySQL Basic operation of database -DQL- The basic query
• The first 8 speak ：MySQL Multi table operation of
• The first 9 speak ：MySQL Aggregate functions 、 Date function 、 Window functions, etc
• The first 10 take ：MySQL View introduction of 、 Create and other operations
• The first 11 speak ：MySQL Stored procedure 、 Features and case exercises
• The first 12 speak ：MySQL Triggers and other operations 、 matters needing attention
• The first 13 speak ：MySQL The index of 、 classification 、 Characteristics, principles and related operations
• The first 14 speak ：MySQL Storage engine classification and operation
• The first 15 speak ：MySQL The business of 、 operation 、 Isolation level
• The first 16 speak ：MySQL Lock mechanism ：MyISAM Table locks 、InnoDB Row lock

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One 、 Introduce

In any database , There are all kinds of logs , It records all aspects of database work , To help the database administrator track all kinds of events that have happened in the database .MySQL No exception .

Two 、 Classification of log

• Error log
• Binary log
• Query log
• Slow query log

3、 ... and 、 Error log

The error log is MySQL One of the most important logs in , It records when mysqld When starting and stopping , As well as information about any serious errors in the running process of the server . When there is any failure of the database that results in the failure of normal use , You can check this log first .

The log is on by default , The default storage directory is mysql Data directory for , The default log file name is hostname.err（hostname It's the host name ）.

View log location instructions ：

show variables like 'log_error%';

Four 、 Binary log -binlog

Binary log （BINLOG） It records all the DDL（ Data definition language ） Statement and DML（ Data manipulation language ） sentence , But it does not include data query statements . This log plays an extremely important role in data recovery in case of disaster ,MySQL Master-slave replication of , Through this binlog Realized .

Binary log ,MySQl8.0 It is on by default , Low version of the MySQL You need to start through the configuration file , And configuration MySQL Format of log .

Windows System ：my.ini Linux System :my.cnf

# Configuration on binlog journal ,  The file prefix of the log is  mysqlbin ----->  The generated file name is as follows  : mysqlbin.000001,mysqlbin.000002
log_bin=mysqlbin

# Configure binary log format 
binlog_format=STATEMENT

Log format

• STATEMENT

The log format is recorded in the log file SQL sentence （statement）, Every one of the items that modify the data SQL Will be recorded in the log file , adopt Mysql Provided mysqlbinlog Tools , You can see the text of each statement clearly . When master and slave copy , Slave Library （slave） Will resolve the log to the original text , And execute it again from the library .

• ROW

The log format records the data changes of each line in the log file , Instead of recording SQL sentence . such as , perform SQL sentence ： update tb_book set status='1' , If it is STATEMENT Log format , A line will be recorded in the log SQL file ; If it is ROW, Because it's updating the whole table , That is to say, every line of record will change ,ROW The data changes of each line will be recorded in the format log .

• MIXED

Mixed up STATEMENT and ROW Two formats .

--  see MySQL Whether it is turned on binlog journal 
show variables like 'log_bin';
 
 
--  see binlog Format of log 
show variables like 'binlog_format';
 
--  Check all the logs 
show binlog events;
 
--  Check out the latest logs 
show master status;
 
--  query-specified binlog journal 
show binlog events in 'binlog.000010';
select * from mydb1.emp2;
select count(*) from mydb1.emp2;
update mydb1.emp2 set salary = 8000;
--  Start at the designated location , View the specified Binlog journal 
show binlog events in 'binlog.000010' from 156;
 
 
--  Start at the designated location , View the specified Binlog journal , Limit the number of queries 
show binlog events in 'binlog.000010' from 156 limit 2;
-- Start at the designated location , With offset , View the specified Binlog journal , Limit the number of queries 
show binlog events in 'binlog.000010' from 666 limit 1, 2;
 
--  Empty all  binlog  Log files 
reset master

5、 ... and 、 Query log

The query log records all the operation statements of the client , Binary log does not contain query data SQL sentence .

By default , The query log is not opened . If you need to open the query log , You can set the following configuration ：

# This option is used to open the query log  ,  Optional value  ： 0  perhaps  1 ; 0  On behalf of closed , 1  Representative opens  
general_log=1

# Set the file name of the log  ,  If not specified ,  The default filename is  host_name.log 
general_log_file=file_name

--  see MySQL Whether the query log is enabled 
show variables like 'general_log';
 
--  Open query log 
set global  general_log=1;
 
select * from mydb1.emp2;
select * from mydb6_view.emp;
 
select count(*) from mydb1.emp2;
select count(*) from mydb6_view.emp;
update mydb1.emp2 set salary = 9000;

6、 ... and 、 Slow query log

The slow query log records that all execution times exceed the parameters long_query_time Set the value and the number of scan records is not less than min_examined_row_limit All of SQL Statement log .long_query_time The default is 10 second , The minimum is 0, The precision can reach microseconds .

#  This parameter is used to control whether the slow query log is turned on ,  Value for ： 1  and  0 , 1  Representative opens , 0  On behalf of closed 
slow_query_log=1

 #  This parameter is used to specify the file name of the slow query log 
slow_query_log_file=slow_query.log

#  This option is used to configure the query time limit ,  Beyond this time will be considered value slow query ,  Will need to log ,  Default 10s

long_query_time=10