On my db server, mysql has 2 gigabytes for temporary tables and yet its
creating 99% of temporary tables on disk.
According to mysqltuner, 99% of temporary tables are created on disk. I've
confirmed this via the "show global status like 'created%'" command. This
is in spite of having the following in my my.cnf:
tmp_table_size = 2G
max_heap_table_size = 2G
I have confirmed these values are really being used via the "show variables
like" command. So there's no typo in my my.cnf. Mysqltuner says "Temporary
table size is already large - reduce result set size" but that is not a
practical suggestion in that none of the programs using the databases on the
server were written by me. I have databases for spamassassin bayesian
rules, horde3 imp (webmail) and moodle on the system. I am not about to try
to modify their code.
I'm running mysql from debian stable (5.0.1). I've double and triple checked
the documentation and it sure looks as if setting tmp_table_size and
max_heap_table_size to be very large should eliminate this problem. But it
doesn't seem to work. I just have to be missing something. But what? My
complete my.cnf is below.
PS: I have another server that is serving only drupal and it too is creating
a high percentage of temp tables on disk (75%). I figure the same setting
is missing and/or wrong on both servers.
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
# This was formally known as [safe_mysqld]. Both versions are currently
parsed.
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0
[mysqld]
#
# * Basic Settings
#
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /srv/mysql
tmpdir = /tmp
language = /usr/share/mysql/english
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address = 127.0.0.1
#
# * Fine Tuning
#
# Commonly used optimization parameters
#
tmp_table_size = 2G
max_heap_table_size = 2G
key_buffer = 2G
max_allowed_packet = 16M
thread_stack = 128K
thread_cache_size = 256
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover = BACKUP
max_connections = 256
table_cache = 1024
thread_concurrency = 16
open_files_limit = 8192
#
# * Query Cache Configuration
#
query_cache_limit = 16M
query_cache_size = 512M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
#log = /var/log/mysql/mysql.log
#
# Error logging goes to syslog. This is a Debian improvement :)
#
# Here you can see queries with especially long duration
# To see slow queries, use 'show processlist'
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 2
log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for
replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
#server-id = 1
#log_bin = /var/log/mysql/mysql-bin.log
expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * BerkeleyDB
#
# Using BerkeleyDB is now discouraged as its support will cease in 5.1.12.
skip-bdb
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
# You might want to disable InnoDB to shrink the mysqld process by circa
100MB.
#skip-innodb
innodb_buffer_pool_size = 2G
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
[mysqldump]
quick
quote-names
max_allowed_packet = 16M
[mysql]
#no-auto-rehash # faster start of mysql but no tab completition
[isamchk]
key_buffer = 16M
#
# * NDB Cluster
#
# See /usr/share/doc/mysql-server-*/README.Debian for more information.
#
# The following configuration is read by the NDB Data Nodes (ndbd processes)
# not from the NDB Management Nodes (ndb_mgmd processes).
#
# [MYSQL_CLUSTER]
# ndb-connectstring=127.0.0.1
#
# * IMPORTANT: Additional settings that can override those from this file!
# The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/
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