1 案例1：MySQL性能优化
1.1 问题
练习相关优化选项
启用慢查询日志
查看各种系统变量、状态变量
1.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：mysql性能优化
1）查看服务运行时的参数配置
mysql> show variables\G;
......
*************************** 171. row ***************************
Variable_name: innodb_log_file_size
Value: 50331648
*************************** 172. row ***************************
Variable_name: innodb_log_files_in_group
Value: 2
*************************** 173. row ***************************
Variable_name: innodb_log_group_home_dir
Value: ./
*************************** 174. row ***************************
Variable_name: innodb_log_write_ahead_size
Value: 8192
*************************** 175. row ***************************
Variable_name: innodb_lru_scan_depth
Value: 1024
*************************** 176. row ***************************
Variable_name: innodb_max_dirty_pages_pct
Value: 75.000000
*************************** 177. row ***************************
Variable_name: innodb_max_dirty_pages_pct_lwm
Value: 0.000000
*************************** 178. row ***************************
Variable_name: innodb_max_purge_lag
Value: 0
......
mysql> show variables like "%innodb%";
+------------------------------------------+------------------------+
| Variable_name | Value |
+------------------------------------------+------------------------+
| ignore_builtin_innodb | OFF |
| innodb_adaptive_flushing | ON |
| innodb_adaptive_flushing_lwm | 10 |
| innodb_adaptive_hash_index | ON |
| innodb_adaptive_hash_index_parts | 8 |
| innodb_adaptive_max_sleep_delay | 150000 |
......
......
| innodb_undo_log_truncate | OFF |
| innodb_undo_logs | 128 |
| innodb_undo_tablespaces | 0 |
| innodb_use_native_aio | ON |
| innodb_version | 5.7.17 |
| innodb_write_io_threads | 4 |
+------------------------------------------+------------------------+
134 rows in set (0.01 sec)
2）并发连接数量
查看当前已经使用的连接数
mysql> flush status;
Query OK, 0 rows affected (0.00 sec)
mysql> show global status like "Max_used_connections";
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| Max_used_connections | 3 |
+----------------------+-------+
1 row in set (0.00 sec)
查看默认的最大连接数
mysql> show variables like "max_connections%";
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 151 |
+-----------------+-------+
1 row in set (0.00 sec)
3）连接超时时间
mysql> show variables like "%timeout%";
+-----------------------------+----------+
| Variable_name | Value |
+-----------------------------+----------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| have_statement_timeout | YES |
| innodb_flush_log_at_timeout | 1 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 28800 |
| lock_wait_timeout | 31536000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| rpl_stop_slave_timeout | 31536000 |
| slave_net_timeout | 60 |
| wait_timeout | 28800 |
+-----------------------------+----------+
13 rows in set (0.00 sec)
4）允许保存在缓存中被重用的线程数量
mysql> show variables like "thread_cache_size";
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| thread_cache_size | 9 |
+-------------------+-------+
1 row in set (0.00 sec)
5）用于MyISAM引擎的关键索引缓存大小
mysql> show variables like "key_buffer_size";
+-----------------+---------+
| Variable_name | Value |
+-----------------+---------+
| key_buffer_size | 8388608 |
+-----------------+---------+
1 row in set (0.00 sec)
6）为每个要排序的线程分配此大小的缓存空间
mysql> show variables like "sort_buffer_size";
+------------------+--------+
| Variable_name | Value |
+------------------+--------+
| sort_buffer_size | 262144 |
+------------------+--------+
1 row in set (0.00 sec)
7）为顺序读取表记录保留的缓存大小
mysql> show variables like "read_buffer_size";
+------------------+--------+
| Variable_name | Value |
+------------------+--------+
| read_buffer_size | 131072 |
+------------------+--------+
1 row in set (0.01 sec)
8）为所有线程缓存的打开的表的数量
mysql> show variables like "table_open_cache";
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| table_open_cache | 2000 |
+------------------+-------+
1 row in set (0.00 sec)
步骤二：SQL查询优化
1）常用日志种类及选项，如图-1所示：
图-1
记录慢查询，图-2所示：
启用慢查询日志
[root@master10 ~]# vim /etc/my.cnf
...
slow_query_log=1
slow_query_log_file=mysql-slow.log
long_query_time=5
log_queries_not_using_indexes=1
...
[root@master10 ~]# systemctl restart mysqld
2）查看慢查询日志
[root@master10 ~]# mysqldumpslow /var/lib/mysql/mysql-slow.log
Reading mysql slow query log from /var/lib/mysql/mysql-slow.log
Count: 1 Time=0.00s (0s) Lock=0.00s (0s) Rows=0.0 (0), 0users@0hosts
查看缓存的大小
mysql> show variables like "query_cache%";
+------------------------------+---------+
| Variable_name | Value |
+------------------------------+---------+
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 1048576 |
| query_cache_type | OFF |
| query_cache_wlock_invalidate | OFF |
+------------------------------+---------+
5 rows in set (0.00 sec)
3）查看当前的查询缓存统计
mysql> show global status like "qcache%";
+-------------------------+---------+
| Variable_name | Value |
+-------------------------+---------+
| Qcache_free_blocks | 1 |
| Qcache_free_memory | 1031832 |
| Qcache_hits | 0 |
| Qcache_inserts | 0 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 40 |
| Qcache_queries_in_cache | 0 |
| Qcache_total_blocks | 1 |
+-------------------------+---------+
8 rows in set (0.00 sec)
