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268 lines
7.8 KiB
Markdown
268 lines
7.8 KiB
Markdown
## mysql
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MySQL 是一个开源的关系型数据库管理系统。
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- 官网: <https://www.mysql.com/>
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- 源码: <https://dev.mysql.com/downloads/file/?id=480541>
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- 文档: <https://dev.mysql.com/doc/refman/5.5/en>
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- 开源: <https://github.com/mysql/mysql-server/tree/5.5>
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## 下载安装
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### Ubuntu安装MySQL
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安装服务器与客户端
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```
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sudo apt-get install mysql-server mysql-client
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```
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相关目录与文件
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- 配置目录 /etc/mysql/
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- 运行状态 /var/run/mysqld/
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- 日志目录 /var/log/mysql/
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- 数据目录 /var/lib/mysql/
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- 其它文件 /var/lib/mysql-files/
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- 动态插件 /usr/lib/mysql/plugin/
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## 基础命令
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初次登录，直接用安装时设置的密码连接
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```
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$ mysql -u root -p
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Enter password
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mysql>
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```
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查看帮助信息
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```
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mysql> help
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...
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```
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其中常用的命令有
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- status 查看当前状态
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- system 调用系统shell命令
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- source 加载并执行sql文件
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- delimiter 设置行分隔符
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- connect 重新连接服务器
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- use 切换数据库
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### 配置操作
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mysql启动时会从/etc/mysql/my.cnf加载配置，show variables;可以查看当前配置
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### 数据库操作
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- 查看 show databases
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- 切换 use demo
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- 创建 create database demo
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- 删除 drop database demo
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查看数据库列表
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```
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mysql> show databases;
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```
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创建数据库
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```
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mysql> create database demo;
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```
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切换数据库
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```
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mysql> use demo;
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```
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删除数据库
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```
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mysql> drop database demo;
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```
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### 关系表操作
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- 查看 show tables
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- 创建 create table demo(a int)
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- 修改 alter table add column b int
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- 查看 desc demo
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- 删除 drop table demo
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### 数据操作
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- 查询 select * from demo
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- 添加 insert into demo values(1,2)
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- 修改 update demo set a=1, b=2 where a=3
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- 删除 delete from demo where a=1
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## 存储引擎
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- 源码：<https://github.com/mysql/mysql-server/tree/5.5/storage>
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- 文档：<https://dev.mysql.com/doc/refman/5.5/en/storage-engines.html>
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```
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mysql> show engines;
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```
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|engine|comment|
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|------|-------|
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|InnoDB| supports transactions, row-level locking, and foreign keys|
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|MyISAM| |
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|MEMORY|hash based, stored in memory, useful for temporary tables|
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|BLACKHOLE| |
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|ARCHIVE| |
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|CSV| |
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|MRG_MYISAM| |
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|PERFORMANCE_SCHEMA| |
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|FEDERATED| |
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### InnoDB
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InnoDB是一种支持ACID事务的存储引擎
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- 源码：<https://github.com/mysql/mysql-server/tree/5.5/storage/innobase>
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- 文档：<https://dev.mysql.com/doc/refman/5.5/en/innodb-storage-engine.html>
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InnoDB是多线程的，通过命令可以看各线程的状态
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```
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mysql> show engine innodb status\G
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```
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|meta|task|
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|------|----|
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|BACKGROUND| 主线程 |
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|FILE I/O| IO线程 |
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|INSERT BUFFER AND HASH INDEX| 插入缓存与哈希索引 |
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|SEMAPHORES| |
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|TRANSACTIONS| |
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|BUFFER POOL AND MEMORY| |
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|ROW OPERATIONS| |
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|LOG| |
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#### 线程与缓存
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MySQL的存储引擎是模块化，所以需要注册模块信息
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```
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// 注册模块 struct st_mysql_plugin {} // mysql-5.5.62/include/mysql/plugin.h:423
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mysql_declare_plugin(innobase) { // mysql-5.5.62/storage/innobase/handler/ha_innodb.cc:11925
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MYSQL_STORAGE_ENGINE_PLUGIN,
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&innobase_storage_engine,
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innobase_hton_name,
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plugin_author,
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"Supports transactions, row-level locking, and foreign keys",
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PLUGIN_LICENSE_GPL,
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innobase_init, /* Plugin Init */
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NULL, /* Plugin Deinit */
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INNODB_VERSION_SHORT,
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innodb_status_variables_export,/* status variables */
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innobase_system_variables, /* system variables */
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NULL, /* reserved */
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0, /* flags */
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}
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...
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mysql_declare_plugin_end;
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```
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InnoDB在初始化函数中，会注册各种回调函数，并启动各种工作线程
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```
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innobase_init() // mysql-5.5.62/storage/innobase/handler/ha_innodb.cc:2218
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// 注册各种回调函数 struct handlerton {} // mysql-5.5.62/sql/handler.h:705
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innobase_hton->state = SHOW_OPTION_YES;
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innobase_hton->db_type= DB_TYPE_INNODB;
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innobase_hton->savepoint_offset=sizeof(trx_named_savept_t);
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innobase_hton->close_connection=innobase_close_connection;
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innobase_hton->savepoint_set=innobase_savepoint;
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innobase_hton->savepoint_rollback=innobase_rollback_to_savepoint;
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innobase_hton->savepoint_release=innobase_release_savepoint;
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innobase_hton->commit=innobase_commit;
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innobase_hton->rollback=innobase_rollback;
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innobase_hton->prepare=innobase_xa_prepare;
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innobase_hton->recover=innobase_xa_recover;
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innobase_hton->commit_by_xid=innobase_commit_by_xid;
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innobase_hton->rollback_by_xid=innobase_rollback_by_xid;
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innobase_hton->create_cursor_read_view=innobase_create_cursor_view;
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innobase_hton->set_cursor_read_view=innobase_set_cursor_view;
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innobase_hton->close_cursor_read_view=innobase_close_cursor_view;
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innobase_hton->create=innobase_create_handler;
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innobase_hton->drop_database=innobase_drop_database;
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innobase_hton->panic=innobase_end;
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innobase_hton->start_consistent_snapshot=innobase_start_trx_and_assign_read_view;
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innobase_hton->flush_logs=innobase_flush_logs;
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innobase_hton->show_status=innobase_show_status;
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innobase_hton->flags=HTON_SUPPORTS_FOREIGN_KEYS;
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innobase_hton->release_temporary_latches=innobase_release_temporary_latches;
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// 启动各种工作线程
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innobase_start_or_create_for_mysql() // srv/srv0start.c:1028
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os_thread_create(io_handler_thread, NULL, NULL);
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os_thread_create(&srv_lock_time_thread, NULL, NULL);
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os_thread_create(&srv_error_monitor_thread, NULL, NULL);
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os_thread_create(&srv_monitor_thread, NULL, NULL);
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os_thread_create(&srv_master_thread, NULL, NULL);
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os_thread_create(&srv_purge_thread, NULL, NULL);
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```
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主线程
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```
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srv_master_thread() // mysql-5.5.62/storage/innobase/srv/srv0srv.c:2748
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loop:
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srv_main_1_second_loops++;
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// 同步日志缓存
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srv_sync_log_buffer_in_background(); // srv/srv0srv.c:2702
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log_buffer_sync_in_background(TRUE); // log/log0log.c:1689
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log_write_up_to(lsn, LOG_NO_WAIT, flush);
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mutex_enter(&(log_sys->mutex));
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log_sys->write_lsn = log_sys->lsn;
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fil_flush(group->space_id); // fil/fil0fil.c:4755
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mutex_enter(&fil_system->mutex);
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os_file_flush(file); // os/os0file.c:2119
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os_file_fsync(file);
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fsync(file);
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// 合并插入缓存
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ibuf_contract_for_n_pages(FALSE, PCT_IO(5));
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// 刷新数据缓存
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buf_flush_list(PCT_IO(100), IB_ULONGLONG_MAX); // buf/buf0flu.c:1928
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buf_flush_batch(buf_pool, BUF_FLUSH_LRU, min_n, 0);
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buf_pool_mutex_enter(buf_pool);
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buf_flush_LRU_list_batch(buf_pool, min_n);
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buf_flush_flush_list_batch(buf_pool, min_n, lsn_limit);
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buf_flush_buffered_writes();
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mutex_enter(&(trx_doublewrite->mutex));
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buf_flush_sync_datafiles();
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// 执行清理任务
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srv_master_do_purge();
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trx_purge(srv_purge_batch_size); // trx/trx0purge.c:1139
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rw_lock_x_lock(&purge_sys->latch);
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thr = que_fork_start_command(purge_sys->query);
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que_run_threads(thr);
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background_loop:
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srv_main_background_loops++;
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row_drop_tables_for_mysql_in_background(); // row/row0mysql.c:2253
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mem_free(drop->table_name);
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flush_loop:
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srv_main_flush_loops++;
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log_checkpoint(TRUE, FALSE); // log/log0log.c:2077
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log_groups_write_checkpoint_info();
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log_group_checkpoint(group);
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suspend_thread:
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srv_suspend_thread(slot);
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```
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- 插入缓存与两次写
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- 自适应哈希索引
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- 启动、恢复、关闭
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- 引擎插件升级
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#### 各种文件
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配置文件，MySQL在启动时会加载配置文件，这些配置在运行时也可以随时读写
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- show variables;
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- show variables like 'timeout';
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- set [global|session] var=val
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日志文件
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数据文件
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### MyISAM
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- 源码：<https://github.com/mysql/mysql-server/tree/5.5/storage/myisam>
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- 文档：<https://dev.mysql.com/doc/refman/5.5/en/myisam-storage-engine.html>
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