La variable système group_concat_max_length n'a pas été modifiée même après avoir changé le fichier my.cnf

Question

J'ai actuellement installé la version MySQL 5.6 installée sur mon système local. Je veux définir définitivement la variable système group_concat_max_length à une certaine valeur. Lorsque je le fais en utilisant la commande set global group_concat_max_len = 100000; dans le terminal mysql, la valeur est définie mais la valeur change par défaut au redémarrage. J'ai également changé le fichier my.cnf et le mettre sous [mysqld] en-tête.

Quelqu'un peut-il suggérer quel pourrait être le problème?

Edit: my.cnf

 

    # 
    # 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  = /var/lib/mysql 
    tmpdir  = /tmp 
    lc-messages-dir = /usr/share/mysql 
    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 


    #max_connections=200 (mysql connections) 
    # 
    # * Fine Tuning 
    # 
    key_buffer  = 16M 
    max_allowed_packet = 16M 
    thread_stack  = 192K 
    thread_cache_size  = 8 
    # This replaces the startup script and checks MyISAM tables if needed 
    # the first time they are touched 
    myisam-recover   = BACKUP 
    #max_connections  = 100 
    #table_cache   = 64 
    #thread_concurrency  = 10 
    # 
    # * Query Cache Configuration 
    # 

    innodb_buffer_pool_size = 8G 
    innodb_flush_log_at_trx_commit = 2 
    query_cache_size=268435456 
    query_cache_type=1 
    query_cache_limit=8388608 
    group_concat_max_len=100000 

    #query_cache_limit = 1M 
    #query_cache_size  = 16M 

    # 
    # * Logging and Replication 
    # 
    # Both location gets rotated by the cronjob. 
    # Be aware that this log type is a performance killer. 
    # As of 5.1 you can enable the log at runtime! 
    #general_log_file  = /var/log/mysql/mysql.log 
    #general_log    = 1 
    # 
    # Error log - should be very few entries. 
    # 
    log_error = /var/log/mysql/error.log 
    # 
    # Here you can see queries with especially long duration 
    #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 
    # 
    # * 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! 
    # 
    # * 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 

    # 
    # * 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/ 

fichier mysql dans /etc/init.d/

 

    ... 
    SELF=$(cd $(dirname $0); pwd -P)/$(basename $0) 
    CONF=/etc/mysql/my.cnf 
    MYADMIN="/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf" 

    # priority can be overriden and "-s" adds output to stderr 
    ERR_LOGGER="logger -p daemon.err -t /etc/init.d/mysql -i" 
    ... 

Après le redémarrage de MySQL:

 

    mysql> show variables like '%group_concat_max%'; 
    +----------------------+-------+ 
    | Variable_name  | Value | 
    +----------------------+-------+ 
    | group_concat_max_len | 1024 | 
    +----------------------+-------+ 
    1 row in set (0.00 sec) 

Answer 1

La seule ligne de votre le fichier de configuration DOIT être listé comme 6 lignes car l'initialisation ne peut traiter qu'une seule variable par ligne, A mon humble avis.

Vous trouverez probablement que la taille de votre cache de requête d'environ 268M et query_cache_limit d'environ 8M serait plus efficace à 50M et 1M respectivement. La raison étant lorsqu'une ligne est modifiée dans une table, chaque résultat de requête mis en cache pour la table mise à jour est marqué comme invalide - c.-à-d. Que les cycles cpu sont consommés pour marquer les résultats de cache individuellement. Après le redémarrage, veuillez confirmer AFFICHER LES VARIABLES GLOBALES COMME 'group_concat_max_length' a votre valeur prévue. Cela devrait être visible.