mysql配置文件my.ini的分析

每天积累一点，菜鸟总得长翅膀的！

这里说的mysql的配置文件是windows下面的。我的版本是5.6，so，如果和你的my.ini有出入，我say sorry。

好！

my.ini咋看起来很震惊人，但是它的注释实在是为我们解决了所有的问题了。《mysql性能调优与架构设计》里面都出现了my.ini里面的英文的译文，所以注释是很好的东西。我们看my.ini里面踢出注释，还剩下以下内容：

[client]port=3306[mysql]default-character-set=latin1[mysqld]# The TCP/IP Port the MySQL Server will listen onport=3306log-error=c:\error.log#Path to installation directory. All paths are usually resolved relative to this.basedir="C:/Program Files/MySQL/MySQL Server 5.0/"#Path to the database rootdatadir="C:/Program Files/MySQL/MySQL Server 5.0/Data/"# The default character set that will be used when a new schema or table is# created and no character set is defineddefault-character-set=utf8# The default storage engine that will be used when create new tables whendefault-storage-engine=INNODB# Set the SQL mode to strictsql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"# The maximum amount of concurrent sessions the MySQL server will# allow. One of these connections will be reserved for a user with# SUPER privileges to allow the administrator to login even if the# connection limit has been reached.max_connections=100# Query cache is used to cache SELECT results and later return them# without actual executing the same query once again. Having the query# cache enabled may result in significant speed improvements, if your# have a lot of identical queries and rarely changing tables. See the# "Qcache_lowmem_prunes" status variable to check if the current value# is high enough for your load.# Note: In case your tables change very often or if your queries are# textually different every time, the query cache may result in a# slowdown instead of a performance improvement.query_cache_size=0# The number of open tables for all threads. Increasing this value# increases the number of file descriptors that mysqld requires.# Therefore you have to make sure to set the amount of open files# allowed to at least 4096 in the variable "open-files-limit" in# section [mysqld_safe]table_cache=256# Maximum size for internal (in-memory) temporary tables. If a table# grows larger than this value, it is automatically converted to disk# based table This limitation is for a single table. There can be many# of them.tmp_table_size=15M# How many threads we should keep in a cache for reuse. When a client# disconnects, the client's threads are put in the cache if there aren't# more than thread_cache_size threads from before.  This greatly reduces# the amount of thread creations needed if you have a lot of new# connections. (Normally this doesn't give a notable performance# improvement if you have a good thread implementation.)thread_cache_size=8#*** MyISAM Specific options# The maximum size of the temporary file MySQL is allowed to use while# recreating the index (during REPAIR, ALTER TABLE or LOAD DATA INFILE.# If the file-size would be bigger than this, the index will be created# through the key cache (which is slower).myisam_max_sort_file_size=100G# If the temporary file used for fast index creation would be bigger# than using the key cache by the amount specified here, then prefer the# key cache method.  This is mainly used to force long character keys in# large tables to use the slower key cache method to create the index.myisam_max_extra_sort_file_size=100G# If the temporary file used for fast index creation would be bigger# than using the key cache by the amount specified here, then prefer the# key cache method.  This is mainly used to force long character keys in# large tables to use the slower key cache method to create the index.myisam_sort_buffer_size=30M# Size of the Key Buffer, used to cache index blocks for MyISAM tables.# Do not set it larger than 30% of your available memory, as some memory# is also required by the OS to cache rows. Even if you're not using# MyISAM tables, you should still set it to 8-64M as it will also be# used for internal temporary disk tables.key_buffer_size=22M# Size of the buffer used for doing full table scans of MyISAM tables.# Allocated per thread, if a full scan is needed.read_buffer_size=64Kread_rnd_buffer_size=256K# This buffer is allocated when MySQL needs to rebuild the index in# REPAIR, OPTIMZE, ALTER table statements as well as in LOAD DATA INFILE# into an empty table. It is allocated per thread so be careful with# large settings.sort_buffer_size=256K#*** INNODB Specific options ***# Use this option if you have a MySQL server with InnoDB support enabled# but you do not plan to use it. This will save memory and disk space# and speed up some things.#skip-innodb# Additional memory pool that is used by InnoDB to store metadata# information.  If InnoDB requires more memory for this purpose it will# start to allocate it from the OS.  As this is fast enough on most# recent operating systems, you normally do not need to change this# value. SHOW INNODB STATUS will display the current amount used.innodb_additional_mem_pool_size=2M# If set to 1, InnoDB will flush (fsync) the transaction logs to the# disk at each commit, which offers full ACID behavior. If you are# willing to compromise this safety, and you are running small# transactions, you may set this to 0 or 2 to reduce disk I/O to the# logs. Value 0 means that the log is only written to the log file and# the log file flushed to disk approximately once per second. Value 2# means the log is written to the log file at each commit, but the log# file is only flushed to disk approximately once per second.innodb_flush_log_at_trx_commit=1# The size of the buffer InnoDB uses for buffering log data. As soon as# it is full, InnoDB will have to flush it to disk. As it is flushed# once per second anyway, it does not make sense to have it very large# (even with long transactions).innodb_log_buffer_size=1M# InnoDB, unlike MyISAM, uses a buffer pool to cache both indexes and# row data. The bigger you set this the less disk I/O is needed to# access data in tables. On a dedicated database server you may set this# parameter up to 80% of the machine physical memory size. Do not set it# too large, though, because competition of the physical memory may# cause paging in the operating system.  Note that on 32bit systems you# might be limited to 2-3.5G of user level memory per process, so do not# set it too high.innodb_buffer_pool_size=40M# Size of each log file in a log group. You should set the combined size# of log files to about 25%-100% of your buffer pool size to avoid# unneeded buffer pool flush activity on log file overwrite. However,# note that a larger logfile size will increase the time needed for the# recovery process.innodb_log_file_size=20M# Number of threads allowed inside the InnoDB kernel. The optimal value# depends highly on the application, hardware as well as the OS# scheduler properties. A too high value may lead to thread thrashing.innodb_thread_concurrency=8log-error=c:\err.loglog=c:\log.log

可以看到，整个文件被[client],[mysql],[mysqld]分成了三部分，所以明白这三部分对应着什么更加重要。

1.[client]下面对应的参数是给客户端读取的，上面的配置文件中，port=3306的设置就是给客户端读取的。

2.[mysql]下面对应的参数是给客户端软件读取的；这里我们默认使用了名称为mysql的客户端，所有这个段，假设我们使用自己写的客户端名称是newMySQL,那么my.ini里面应该有[newMySQL]段；

  所以可以说：[client]下面的参数是所有mysql客户端都可以读取的参数，[mysql]是名称为mysql的客户端可以读取的参数；

3.[mysqld]下面对应的参数是最多的，这里面的参数是mysql服务器使用的，例如要改变新建的数据库的默认字符集，可以将[mysqld]字段下面的default-character-set设置为utf8，即default-character-set=utf8。注意了，[mysql]里面也有这个参数的设置哦，所以请区别好段。

好，理解了上面对三个中括号段的说明，我们应该在哪里设置就很明确了，同时为什么在那里设置也就很好回答了。至于参数的含义就不说了，注释很清楚。