- This topic is for my.cnf Configuration to do a detailed description of the parameters
- The sample configuration is as follows ：
- #cat my.cnf
- # MySQL client library initialization.
- = 3306
- socket = /tmp/mysql.sock
- character-set-server = utf8
- # The MySQL server
- init_connect = 'set names utf8'// Set connection mysql Database utf8 code , In order to let mysql Database to utf8 function
- >show variables like'character%'\G; Can query mysql Character related
- init_connect = 'SET autocommit=0' // Turn off auto submit mode , Think that users always operate in a transactional way
- character-set-server = utf8
- port = 3306
- socket = /tmp/mysql.sock
- basedir = /opt/justone/mysqldM/mysql
- datadir = /opt/justone/mysqldM/mysql/data
- skip-locking // avoid MySQL External locking of , Reduce the chance of error and increase stability .
- #skip-networking// Turn this option on to turn it off completely MySQL Of TCP/IP How to connect , If WEB The server is accessed remotely MySQL Do not turn on the database server ！ Otherwise, you will not be able to connect properly ！
- skip_name_resolve// prohibit MySQL For external connections DNS analysis , Use this option to eliminate MySQL Conduct DNS Time of resolution . If this option is turned on , Then all remote host connection authorizations must use IP Address , otherwise MySQL Connection requests will not be processed properly ！
- #back_log = 384 // The number of connections that can be held in the listening queue is saved in MySQL The connection manager thread handles previous connections .
- back_log The value of the parameter is indicated in MySQL How many requests can be stored in the stack in a short time before the response to a new request is temporarily stopped .
- If there are many connections in a short time , You need to increase the value of this parameter , To designate the coming TCP/IP The size of the listening queue for the connection .
- Different operating systems have their own limits on the size of this queue . Try to set back_log Higher than the limit of your operating system will be invalid .
- The default value is 50. about Linux The system recommended setting is less than 512 The integer of . The system value is determined by ulimit-a see .
- max_connections = 2000 // The number of customers allowed at the same time . Increasing this value increases mysqld Number of file descriptors required .
- notes ： The value is too small , Clients often have Too many connections error .
- wait_timeout=10 // Specify the maximum connection time for a request , about 4GB Left and right memory servers can be set to 5-10.
- max_connect_errors = 500 // The same host has the number of broken connection errors exceeding the value of this parameter , Then the host will be forbidden to connect .
- If the host needs to be released , perform ：FLUSH HOST;
- table_open_cache = 2048 // Number of open tables for all threads
- max_allowed_packet = 16M// The maximum size of a query statement package , The allowable size of packets used in information exchange ( Such as ： The import table )
- max_heap_table_size = 256M //HEAP Data sheet ( Memory tables ) Maximum length of ( The default setting is 16M);
- Over this length HEAP The data table will be stored in a temporary file instead of staying in memory .
- sort_buffer_size = 512K // The size of the buffer that can be used when querying the sort .
- The allocated memory corresponding to this parameter is exclusive per connection , if there be 100 A connection , The actual allocated sort buffer size is 100×512K＝50MB.
- therefore , For memory in 4GB The recommended settings for the left and right servers are 6-8M.
- join_buffer_size = 1M // The size of the buffer that can be used by the federated query operation , The allocated memory corresponding to this parameter is also exclusive for each connection .
- thread_cache_size = 8 // The number of threads that can be reused and stored in the thread cache . Memory G*8 namely 2G Set to 16
- Each connection to the database uses its own thread . Thread creation takes time , So if the thread doesn't need to be closed when the connection is closed , The server keeps it in its own thread cache , For the next connection to use .
- thread_concurrency = 8 // The value of this parameter is server logic CPU Number ×2
- bulk_insert_buffer_size = 8M // Appoint MyISAM Type tables use special tree structured caching .
- Use the block approach (bulk) Can speed up the insertion operation ( INSERT … SELECT, INSERT …VALUES (…), (…), …, and LOAD DATA INFILE) Speed and efficiency . This parameter limits the size of the tree cache used by each thread , If set to 0 The cache acceleration function is disabled . Be careful ： The cache operation corresponding to this parameter can only be sent to non empty users Insert operations in data tables ！ The default value is 8MB.
- query_cache_size = 64M // Appoint MySQL Query buffer size .
- It can be done by MySQL The console performs the following commands to observe ：
- > SHOW VARIABLES LIKE'%query_cache%';
- > SHOW STATUS LIKE'Qcache%';
- Qcache_lowmem_prunes It's worth a lot , It indicates that insufficient buffer often occurs ;
- Qcache_hits It's worth a lot , It shows that query buffer is used very frequently , If the value is small, it will affect the efficiency , So we can consider not to query buffer ;
- Qcache_free_blocks, If the value is very large , It indicates that there are many fragments in the buffer .
- default-storage-engine = InnoDB // The default data table type for the new data table The default setting is MyISAM
- lower_case_table_names = 1 //MySQL Implementation is case insensitive
- transaction_isolation = REPEATABLE-READ // Set the default transaction isolation level for all connections
- tmp_table_size = 256M // temporary HEAP The maximum length of the data table
- The default setting is 32M; Temporary tables over this length will be converted to MyISAM Data table and save it in a temporary file .
- slow_query_log = 1
- log = /opt/justone/mysqldM/mysql/logs/mysql.log
- long_query_time = 2
- log-slow-queries =/opt/justone/mysqldM/mysql/logs/slowquery.log
- # Replication related settings
- server-id = 1 // Set to master
- log-bin=mysql-bin // Produced log With mysql-bin start
- binlog_cache_size = 8M // by binary log Specifies that during query request processing SQL The size of the cache used by the query statement .
- If it is frequently applied to a large number of 、 complex SQL Expression processing , The value of this parameter should be increased for performance improvement .
- binlog_format=mixed // Log format , You can also customize .
- InnoDB and MyISAM Type difference
- InnoDB and MyISAM It's used by a lot of people MySQL , the two most commonly used table types , Each of these table types has its advantages and disadvantages , It depends on the application .
- The basic difference is ：MyISAM Types do not support advanced processing such as transaction processing , and InnoDB Type of support .
- MyISAM Type tables emphasize performance , The ratio of execution InnoDB The type is faster , Transaction support is not provided , and InnoDB Provides advanced database functions such as transaction support and external keys .
- InnoDB What to pay attention to ：
- 1.InnoDB I won't support it FULLTEXT Index of type .
- 2.InnoDB The specific number of rows of the table is not saved in , in other words , perform select count(*) fromtable when ,InnoDB Scan the entire table to see how many rows there are , however MyISAM Simply read out the number of saved lines . Pay attention to is , When count(*) language Sentence contains where When the conditions , The operation of the two kinds of tables is the same .
- 3. about AUTO_INCREMENT Type field ,InnoDB Must contain only the index of this field , But in MyISAM In the table , You can create a union index with other fields .
- 4.DELETE FROMtable when ,InnoDB The table will not be recreated , It's line by line deletion .
- 5.LOAD TABLE FROMMASTER Operation of InnoDB It doesn't work , The solution is to put InnoDB Change the watch to MyISAM surface , Import the data and change it to InnoDB surface , But for the extra InnoDB characteristic （ For example, foreign key ） The table of does not apply .
- 6.InnoDB The row lock of the table is not absolute either , If you are executing a SQL When the sentence is MySQL Can't determine the range to scan ,InnoDB The watch also locks the whole watch , for example updatetable set num=1 where name like “?a%”
- # MyISAM Specific options
- key_buffer_size = 32M // Buffer size of index block , Add it to get better indexes ( For all reading and rewriting )
- The index block is buffered and shared by all threads . If you make it too big , The system will start to change pages and really slow down .
- The default value is 8388600(8M),MySQL The main engine has 2GB Memory , May be set as 402649088(400MB).
- Be careful ： If the parameter value is set too large, the overall efficiency of the server will be reduced ！
- read_buffer_size = 256K // The size of the buffer that can be used for read query operations , The allocated memory corresponding to this parameter is also exclusive for each connection .
- read_rnd_buffer_size = 256K // In a certain order ( Such as ORDERBY Clause ) Output query results ( Default 256K)
- Speed up reading data after sorting operation , Speed up reading classified lines .
- myisam_sort_buffer_size = 128M //myisam Engine sort_buffer_size
- myisam_max_sort_file_size = 10G // It's similar to
- myisam_recover // Auto check and repair doesn't shut down properly MyISAM surface
- #skip-innodb // Get rid of innodb Support
- #skip-bdb // Get rid of bdb Transactional tables support
- # INNODB Specific options ***
- innodb_additional_mem_pool_size = 16M//InnoDB Memory pool size used to store data dictionaries and other internal data structures .
- The more tables in an application, the more memory should be allocated , If innodb If you run out of memory, you will ask for the system memory .
- And write the warning log , according to MySQL manual , about 2G Memory machine , Recommended value is 20M.
- The default value is 1M. Usually not too big , As long as it's enough , It has to do with the complexity of the table structure .
- #innodb_buffer_pool_size = 6G // Specify the size of memory to buffer data and indexes .
- For the individual MySQL database server , The maximum value can be set to physical memory 80%.
- according to MySQL manual , about 2G Memory machine , Recommended value is 1G（50%）
- innodb_buffer_pool_size = 512M
- innodb_data_file_path = ibdata1:10M:autoextend// To hold InnoDB Is the table space of the data table :
- More than one document may be involved ; The maximum length of each table space file must be in bytes (B)、 Megabytes (MB) Or gigabytes (GB) Given in units ;
- The names of the table space files must be separated by semicolons ; The last table space file can also carry a autoextend Property and a maximum length (max:n).
- for example ,ibdata1:1G;ibdata2:1G:autoextend:max:2G It means :
- Table space files ibdata1 The maximum length of is 1GB,ibdata2 And the maximum length of it is also 1G, But allow it to expand to 2GB.
- except Outside the file name , You can also define the table space with the setting name of the hard disk partition , At this point, you must add... To the maximum initial length of the table space newraw Keywords do suffixes , Add... To the maximum extended length of the table space raw Keywords do suffixes ( for example /dev/hdb1:20Gnewraw or /dev/hdb1:20Graw);MySQL 4.0 The default settings for version 1 and later are ibdata1:10M:autoextend.
- innodb_file_io_threads = 4 //IO operation ( Hard disk write operations ) The maximum number of threads ( The default setting is 4).
- innodb_file_per_table = 1// Create a table space file for each new table instead of saving all tables in a central table space
- If there are not many tables in the system , And there's no big watch , Use this parameter to make the , Maintenance is relatively independent .
- innodb_thread_concurrency = 16//InnoDB The maximum number of threads that the driver can use at the same time ( The default setting is 8).
- innodb_flush_log_at_trx_commit = 1 //InnoDB How to log .
- If set to 1, When each transaction is committed ,MySQL Will write the transaction log to disk .
- If set to 0 perhaps 2, The log is written to disk approximately once per second .
- Actual test findings , This value has a great influence on the speed of inserting data
- Set to 2 Insert when 10000 Records only need 2 second , Set to 0 When it comes to 1 second , And set to 1 When you need 229 second .
- It is recommended to merge the insert operations into one transaction as much as possible , This can greatly speed up .
- In the presence of the risk of losing the most recent part of the transaction , You can set this value to 0.
- innodb_log_buffer_size = 8M // The size of the log cache
- The default setting is in the case of medium write load and short transactions , Generally, it can meet the performance requirements of the server .
- If the update operation peak or load is large, you should increase this value .8-16M that will do .
- innodb_log_file_size = 256M // The size of each log file in the log group is very important in the case of high write load, especially in the case of large data sets .
- The higher the value, the higher the performance , But it takes longer to recover . The default is 5M.Javaeye recommend innodb_log_file_size = 64M
- It should be noted that After modification, we need to STOP The service then removes the original log ib_logfile0 and ib_logfile1, And then start the service .
- Overall performance analysis report > show engine innodbstatus\G;
- innodb_log_files_in_group = 3 // Number of log files in log group , Recommended 3
- innodb_max_dirty_pages_pct = 90 // Percentage of maximum dirty pages
- When the percentage of dirty pages in the system exceeds this value ,INNODB A write operation is performed to write the updated data in the page to the disk file .
- innodb_flush_method = O_DIRECT//InnoDB Log file synchronization method ( Only applicable to UNIX/Linux System ).
- O_DIRECT Skipping the file system of the operating system DiskCache, Give Way MySQL Direct read write disk .
- innodb_lock_wait_timeout = 120 // Transaction get resource timeout , Default 50s
- If a transaction is waiting n second (s) We haven't got the resources we need yet , Just use ROLLBACK Order to abort the transaction .
- This setting is not available for discovery and processing InnoDB The deadlock condition identified by the data table driver is of great significance .
- But it can't automatically monitor the deadlock caused by table lock .
- quick // Do not buffer queries , Export directly to stdout; Use mysql_use_result() Do it .
- Don't cache the entire result in memory before writing it to disk . This is required when exporting very large tables
- max_allowed_packet = 16M
- no-auto-rehash // Do not auto fill command , Set up auto-rehash For automatic completion . Default TAB A filling
- #safe-updates // Only key values are allowed UPDATE and DELETE
- [myisamchk] //MyISAM Table maintenance is a very practical tool .
- have access to myisamchk Utility to get information about database tables or check 、 Repair 、 Optimize them .
- myisamchk apply MyISAM surface ( Corresponding .MYI and .MYD A list of documents ).
- key_buffer_size = 512M
- sort_buffer_size = 512M
- read_buffer = 8M
- write_buffer = 8M
- interactive-timeout // Set the maximum amount of time for a data transfer to the default 28800 second
- open-files-limit = 8192 // Number of openable files per process .
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