MySQL: Difference between revisions

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== Documentation ==
= Links =
 
*[https://downloads.mysql.com/archives/community/ Downloads]
 
*[https://dev.mysql.com/doc/mysql-apt-repo-quick-guide/en/ A Quick Guide to Using the MySQL APT Repository]
 
 
 
= Documentation =


*[http://www.mysql.com/ Homepage]  
*[http://www.mysql.com/ Homepage]  
Line 17: Line 25:
*[https://blog.monyog.com/top-10-things-to-monitor-on-your-mysql-server/ 10 things to monitor on your mysql server]  
*[https://blog.monyog.com/top-10-things-to-monitor-on-your-mysql-server/ 10 things to monitor on your mysql server]  
*[[MySQL_Replication|MySQL Replication]]  
*[[MySQL_Replication|MySQL Replication]]  
*[https://mariadb.com/kb/en/mariadb-error-codes/ Mariadb error codes]
*[https://dev.mysql.com/doc/mysql-errors/8.0/en/client-error-reference.html Client error reference]


[https://serverfault.com/questions/202000/how-find-and-fix-fragmented-mysql-tables Fragmented tables]
*[https://serverfault.com/questions/202000/how-find-and-fix-fragmented-mysql-tables Fragmented tables]  


 
 
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  [https://dev.mysql.com/doc/refman/8.0/en/data-types.html https://dev.mysql.com/doc/refman/8.0/en/data-types.html]
  [https://dev.mysql.com/doc/refman/8.0/en/data-types.html https://dev.mysql.com/doc/refman/8.0/en/data-types.html]


== Tools ==
 
 
 
 
= Tools =


*[http://www.adminer.org/ http://www.adminer.org/]  
*[http://www.adminer.org/ Adminer] ('''check out!''' )
*phpmyadmin  
*[[Phpmyadmin|phpmyadmin]]
*[http://phpminiadmin.sourceforge.net/ http://phpminiadmin.sourceforge.net/]  
*[http://phpminiadmin.sourceforge.net/ http://phpminiadmin.sourceforge.net/]  
*[https://www.mysqlcalculator.com/ MySQL memory calculator]  
*[https://www.mysqlcalculator.com/ MySQL memory calculator]  


=== Create a diagram ===
== Create a diagram ==


*[http://plindenbaum.blogspot.com/2008/10/creating-dia-diagrams-from-mysql-via.html Create a dia diagram]  
*[http://plindenbaum.blogspot.com/2008/10/creating-dia-diagrams-from-mysql-via.html Create a dia diagram]  


=== Show syntax ===
== Show syntax ==


[http://dev.mysql.com/doc/refman/5.1/en/show.html http://dev.mysql.com/doc/refman/5.1/en/show.html]
[http://dev.mysql.com/doc/refman/5.1/en/show.html http://dev.mysql.com/doc/refman/5.1/en/show.html]


=== Tuning MySQL ===
== Tuning MySQL ==


*[http://www.mysqlperformanceblog.com/ http://www.mysqlperformanceblog.com/]  
*[http://www.mysqlperformanceblog.com/ http://www.mysqlperformanceblog.com/]  
Line 63: Line 77:
*[http://www.ibm.com/developerworks/web/library/l-tune-lamp-3.html Tuning MysQL]  
*[http://www.ibm.com/developerworks/web/library/l-tune-lamp-3.html Tuning MysQL]  


 
== Benchmarking ==
=== mysqlslap ===
*[https://dev.mysql.com/doc/refman/8.0/en/mysqlslap.html mysqlslap documentation]
 
=HOWTO=
==Reset auto increment==
ALTER TABLE tablename AUTO_INCREMENT = 1
= FAQ =
==Finding mysql configuration files==
===On Ubuntu===
mysqld: /etc/mysql/mysql.conf.d/mysqld.cnf
==ERROR 1231 (42000): Variable 'slow_query_log_file' can't be set to the value of '/var/log/mysql-slow.log'==
Means the file doesn't exist, create it and chown mysql.mysql ( or similar )
==Accounts==
https://dev.mysql.com/doc/refman/8.0/en/show-grants.html
show grants
revoke
===Set password to user on auth_socket===
This just changes from auth_socket to password
alter user 'root'@'localhost' identified with caching_sha2_password by 's3cr37';
flush privileges;
== change password ==
alter user 'foo'@'localhost' identified by 's3cr3t5';


seems this no longer works on ubuntu/mysql8? nor does


mysqladmin -u root --password


== FAQ ==


=== Clustering ===
== Clustering ==


Check out percona galera (and xtrabackup)
Check out percona galera (and xtrabackup)


==Misc==
=== server went away ===
=== server went away ===


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=== change password ===
 
 
alter user 'foo'@'localhost' identified by 's3cr3t5';


=== stop query ===
=== stop query ===
Line 89: Line 136:
 
 


=== change rights ===
=== InnoDB: Error: log file ./ib_logfile0 is of different size 0 5242880 bytes ===
 
(re)move ib_logfile[01]
 
 
 


=== run query in script ===
=== run query in script ===
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  SHOW ENGINE INNODB STATUS
  SHOW ENGINE INNODB STATUS


=== restore single table from backup ===
 
 
{


=== mysql error codes ===
=== mysql error codes ===
Line 161: Line 211:


 
 
 
== mysqldump ==


=== separate lines in mysqldump ===
=== separate lines in mysqldump ===
Line 166: Line 220:
  --extended-insert=FALSE --complete-insert=TRUE  
  --extended-insert=FALSE --complete-insert=TRUE  


=== Fix privileges ===
=== maximum statement execution time exceeded when dumping table ===
 
  max_execution_time
  mysql_fix_privilege_tables


=== mysqldump: out of memory ===
=== mysqldump: out of memory ===


  mysqldump -q
  mysqldump -q
=== mysqldump: Got error: 1040: Too many connections when trying to connect ===
=== mysqldump: MySQL server has gone away (2006) ===
seems related to max_allowed_packet [[File:Example.jpg|RTENOTITLE]]
===mysqldump: Dumping 'information_schema' DB content is not supported===
Just don't try to dump it :)
===Warning: /usr/bin/mysqldump: ignoring option '--databases' due to invalid value 'mysql'===
Check your ~/.my.cnf
== Other stuff ==
=== Fix privileges ===
mysql_fix_privilege_tables


 
 
Line 181: Line 252:
  purge binary logs to 'mysql-bin.xxxyy';
  purge binary logs to 'mysql-bin.xxxyy';


 
=== mysqldump: Got error: 1040: Too many connections when trying to connect ===
=== mysqldump: MySQL server has gone away (2006) ===
seems related to max_allowed_packet [[File:Example.jpg|RTENOTITLE]]


 


=== ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 0 ===
=== ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 0 ===
Line 203: Line 266:
will probably provide clues, it might well be a matter of reducing load/qps
will probably provide clues, it might well be a matter of reducing load/qps


=== error 1146 Table 'performance_schema.session_variables' doesn't exist SQL=SHOW VARIABLES LIKE "collation_database" ===
=== error 1146 Table 'performance_schema.session_variables' doesn't exist ===


Run mysql_upgrade and restart mysqld
Run mysql_upgrade and restart mysqld
== ERROR 1410 (42000): You are not allowed to create a user with GRANT ==
Maybe you got wrong host for the user, like 'localhost' instead of '%'


=== show table sizes ===
=== show table sizes ===
Line 212: Line 279:


 
 
==show database sizes==
SELECT table_schema "DB Name", ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" FROM
information_schema.tables
GROUP BY table_schema;


=== InnoDB: page_cleaner: 1000ms intended loop took 16955ms. The settings might not be optimal. ===
=== InnoDB: page_cleaner: 1000ms intended loop took 16955ms. The settings might not be optimal. ===
Line 217: Line 289:
  ???
  ???


 


=== ERROR 1010 (HY000): Error dropping database (can't rmdir './foo', errno: 39) ===
=== ERROR 1010 (HY000): Error dropping database (can't rmdir './foo', errno: 39) ===
Files in $datadir/foo mysql doesn't know about
Files in $datadir/foo mysql doesn't know about


 
 
=== privileges for SHOW GLOBAL STATUS ===
CREATE USER 'zbx_monitor'@'localhost' IDENTIFIED BY '<password>';
GRANT REPLICATION CLIENT,PROCESS,SHOW DATABASES,SHOW VIEW ON *.* TO 'zbx_monitor'@'localhost';


=== Check fragmentation ===
=== Check fragmentation ===
Line 234: Line 313:
  WHERE DATA_FREE > 0
  WHERE DATA_FREE > 0
  ORDER BY frag_ratio DESC;
  ORDER BY frag_ratio DESC;
  [[Category:Pages with broken file links]]


== Show processes ==
== Show processes ==

Revision as of 15:31, 30 November 2022

Links


Documentation

 

Data types

https://dev.mysql.com/doc/refman/8.0/en/data-types.html

 

 

Tools

Create a diagram

Show syntax

http://dev.mysql.com/doc/refman/5.1/en/show.html

Tuning MySQL

In my.cnf check out:

log_slow_queries

On prompt check out stuff like:

SHOW STATUS LIKE '%qcache%';
SHOW GLOBAL STATUS;
SHOW VARIABLES;

 

 

Benchmarking

mysqlslap

 

HOWTO

Reset auto increment

ALTER TABLE tablename AUTO_INCREMENT = 1

FAQ

Finding mysql configuration files

On Ubuntu

mysqld: /etc/mysql/mysql.conf.d/mysqld.cnf

ERROR 1231 (42000): Variable 'slow_query_log_file' can't be set to the value of '/var/log/mysql-slow.log'

Means the file doesn't exist, create it and chown mysql.mysql ( or similar )

Accounts

https://dev.mysql.com/doc/refman/8.0/en/show-grants.html

show grants
revoke 

Set password to user on auth_socket

This just changes from auth_socket to password

alter user 'root'@'localhost' identified with caching_sha2_password by 's3cr37';
flush privileges;

change password

alter user 'foo'@'localhost' identified by 's3cr3t5';

seems this no longer works on ubuntu/mysql8? nor does

mysqladmin -u root --password


Clustering

Check out percona galera (and xtrabackup)

Misc

server went away

  • can be triggered by max_packet_size

 

 

stop query

show processlist
kill <id of query>

 

InnoDB: Error: log file ./ib_logfile0 is of different size 0 5242880 bytes

(re)move ib_logfile[01]

 


run query in script

RES=`mysql -qsBe "select foo from fu.bar where tap ='beer'" -N`

where did mysql_config_editor go?

https://mariadb.com/resources/blog/mysql-56-security-through-complacency explains how no security is better than some security

high memory usage

fix logrotate on debian

echo "SET PASSWORD FOR 'debian-sys-maint'@'localhost' = PASSWORD('`grep password /etc/mysql/debian.cnf | head -n 1 | awk -F= '{ gsub(/[ \t]+/, "", $2); print $2 }'`');" | mysql -u root -p

insert select

 insert into bar(c,d) select concat ("foo ",w) as  c, concat("bar ",w) as d from foo;

 

slow imports

https://support.tigertech.net/mysql-large-inserts

speed up import from dump

SET autocommit=0;
SET unique_checks=0;
SET foreign_key_checks=0;

and after import

COMMIT;
SET autocommit=1;
SET unique_checks=1;
SET foreign_key_checks=1;

and turn them back on

and try mysqldump --extended-insert (this seems to be default now, and part of --opt)

pagination in CLI

show tables;\P less

show mysql configuration

show variables

 

show performance

show innodb status

or

SHOW ENGINE INNODB STATUS

 

mysql error codes

http://dev.mysql.com/doc/refman/5.1/en/error-messages-client.html

 

 

mysqldump

separate lines in mysqldump

--extended-insert=FALSE --complete-insert=TRUE 

maximum statement execution time exceeded when dumping table

max_execution_time

mysqldump: out of memory

mysqldump -q

mysqldump: Got error: 1040: Too many connections when trying to connect

mysqldump: MySQL server has gone away (2006)

seems related to max_allowed_packet RTENOTITLE

mysqldump: Dumping 'information_schema' DB content is not supported

Just don't try to dump it :)

Warning: /usr/bin/mysqldump: ignoring option '--databases' due to invalid value 'mysql'

Check your ~/.my.cnf

Other stuff

Fix privileges

mysql_fix_privilege_tables

 

clean up mysql-bin

purge logs;
purge binary logs to 'mysql-bin.xxxyy';


ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 0

Could be /etc/hosts.allow

ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

SHOW ENGINE INNODB STATUS

will probably provide clues, it might well be a matter of reducing load/qps

error 1146 Table 'performance_schema.session_variables' doesn't exist

Run mysql_upgrade and restart mysqld

ERROR 1410 (42000): You are not allowed to create a user with GRANT

Maybe you got wrong host for the user, like 'localhost' instead of '%'

show table sizes

SELECT table_schema as `Database`, table_name AS `Table`, round(((data_length + index_length) / 1024 / 1024), 2) `Size in MB`  FROM information_schema.TABLES  ORDER BY (data_length + index_length) DESC;

 

show database sizes

SELECT table_schema "DB Name", ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" FROM 
information_schema.tables 
GROUP BY table_schema; 

InnoDB: page_cleaner: 1000ms intended loop took 16955ms. The settings might not be optimal.

???

 

ERROR 1010 (HY000): Error dropping database (can't rmdir './foo', errno: 39)

Files in $datadir/foo mysql doesn't know about

 

privileges for SHOW GLOBAL STATUS

CREATE USER 'zbx_monitor'@'localhost' IDENTIFIED BY '<password>';
GRANT REPLICATION CLIENT,PROCESS,SHOW DATABASES,SHOW VIEW ON *.* TO 'zbx_monitor'@'localhost';

Check fragmentation

select ENGINE,
 concat(TABLE_SCHEMA, '.', TABLE_NAME) as table_name,
 round(DATA_LENGTH/1024/1024, 2) as data_length,
 round(INDEX_LENGTH/1024/1024, 2) as index_length,
 round(DATA_FREE/1024/1024, 2) as data_free,
 (data_free/(index_length+data_length)) as frag_ratio
FROM information_schema.tables
WHERE DATA_FREE > 0
ORDER BY frag_ratio DESC;

Show processes

SELECT * from INFORMATION_SCHEMA.PROCESSLIST
show full processlist

Tips & Tricks

save password

 mysql_config_editor set --host=localhost --user=root --password

(due to serious crappiness you might have to quote the password)

On newer versions this no longer works, and you have to fall back to using ~/.my.cnf

[client]
user=root
password=s3cr3t

set pager

pager less;

and to disable it again:

nopager;