技术分享 | MySQL 巡检

sar -u 10 3 

 sar -r 10 3

sar -b 10 3

df -h

tail 200 /var/log/messages
dmesg | tail 200

\s
show full processlist;
show engine innodb status\G
show slave hosts;

show global status like 'Innodb_buffer_pool_wait_free';
show global status like 'Innodb_log_waits';

#表锁
show global status like 'Table_locks_waited';
show global status like 'Table_locks_immediate';

#行锁
show global status like 'Innodb_row_lock_current_waits';当前等待锁的行锁数量
show global status like 'Innodb_row_lock_time';请求行锁总耗时
show global status like 'Innodb_row_lock_time_avg';请求行锁平均耗时
show global status like 'Innodb_row_lock_time_max';请求行锁最久耗时
show global status like 'Innodb_row_lock_waits';行锁发生次数

#还可以定时收集INFORMATION_SCHEMA里面的信息：

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS; 
SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS; // MySQL 8.0 中已经不再使用，建议观测 sys 库
#临时表/临时文件
show global status like 'Created_tmp_disk_tables';
show global status like 'Created_tmp_files';

#打开表/文件数
show global status like 'Open_files';
show global status like 'Open_table_definitions';
show global status like 'Open_tables';

#并发连接数
show global status like 'Threads_running';
show global status like 'Threads_created';
show global status like 'Threads_cached';
show global status like 'Aborted_clients';
 
#客户端没有正确关闭连接导致客户端终止而中断的连接数
show global status like 'Aborted_connects';

# 使用临时二进制日志缓存但超过 binlog_cache_size 值，需要使用临时文件存储事务中的语句的事务数
binlog_cache_disk_use;

# 使用二进制日志缓存的事务数
binlog_cache_use;

# 使用二进制日志语句缓存但超过 binlog_stmt_cache_size 的值，需要使用临时文件存储这些语句的非事务语句的数量
binlog_stmt_cache_disk_use;

# 使用二进制日志语句缓存的非事务性语句的数量
binglog_cache_disk_use;

# 试图连接到（不管成不成功）mysql服务器的链接数
show global status like 'Connection'; 

# 服务器执行语句时,在硬盘上自动创建的临时表的数量,是指在排序时,内存不够用(tmp_table_size小于需要排序的结果集)，所以需要创建基于磁盘的临时表进行排序
show global status like 'Created_tmp_disk_tables'; 

# 服务器执行语句时自动创建的内存中的临时表的数量
show global status like 'Created_tmp_files';

# 内部提交语句
show global status like 'Handler_commit'; 

# 内部 rollback语句数量
show global status like 'Handler_rollback'; 

# 索引第一条记录被读的次数,如果高,则它表明服务器正执行大量全索引扫描
show global status like 'Handler_read_first';  

# 根据索引读一行的请求数，如果较高，说明查询和表的索引正确
show global status like 'Handler_read_key'; 

# 查询读索引最后一个索引键请求数
show global status like 'Handler_read_last';

# 按照索引顺序读下一行的请求数
show global status like 'Handler_read_next'; 

# 按照索引顺序读前一行的请求数
show global status like 'Handler_read_prev';

# 根据固定位置读一行的请求数，如果值较高，说明可能使用了大量需要mysql扫整个表的查询或没有正确使用索引
show global status like 'Handler_read_rnd'; 

# 在数据文件中读下一行的请求数，如果你正进行大量的表扫，该值会较高
show global status like 'Handler_read_rnd_next'; 

# 被缓存的.frm文件数量
show global status like 'Open_table_definitions'; 

# 已经打开的表的数量,如果较大,table_open_cache值可能太小
show global status like 'Opened_tables';

# 当前打开的表的数量
show global status like 'Open_tables';

# 已经发送给服务器的查询个数
show global status like 'Queries';

# 没有使用索引的联接的数量,如果该值不为0,你应该仔细检查表的所有
show global status like 'Select_full_join';

# 对第一个表进行完全扫的联接的数量
show global status like 'Select_scan';

# 查询时间超过long_query_time秒的查询个数
show global status like 'Slow_queries';

# 排序算法已经执行的合并的数量,如果值较大,增加sort_buffer_size大小
show global status like 'Sort_merge_passes';

# 线程缓存内的线程数量
show global status like 'Threads_cached';

# 当前打开的连接数量
show global status like 'Threads_connected';

# 创建用来处理连接的线程数
show global status like 'Threads_created';

# 激活的（非睡眠状态）线程数
show global status like 'Threads_running';

SELECT
 table_schema,
 table_name,
 ENGINE,
 Auto_increment 
FROM
 information_schema.TABLES 
WHERE
 TABLE_SCHEMA NOT IN (
  "INFORMATION_SCHEMA",
  "PERFORMANCE_SCHEMA",
 "MYSQL",
 "SYS") limit 30;

SELECT
 table_schema "Database name",
 sum( table_rows ) "No. of rows",
 sum( data_length ) / 1024 / 1024 "Size data (MB)",
 sum( index_length )/ 1024 / 1024 "Size index (MB)" 
FROM
 information_schema.TABLES 
GROUP BY
 table_schema;

SELECT 
    TABLE_SCHEMA,
    TABLE_NAME,
    TABLE_ROWS
FROM 
    `information_schema`.`tables` 
WHERE
    TABLE_SCHEMA not in('information_schema','sys','mysql','performance_schema')
ORDER BY table_rows DESC LIMIT 30;

SELECT
 TABLE_SCHEMA,
 TABLE_NAME,
ENGINE 
FROM
 INFORMATION_SCHEMA.TABLES 
WHERE
 ENGINE != 'innodb' 
 AND TABLE_SCHEMA NOT IN ( "INFORMATION_SCHEMA", "PERFORMANCE_SCHEMA", "MYSQL", "SYS" );

select 
    TABLE_SCHEMA,
    TABLE_NAME,
    TABLE_ROWS,
    DATA_LENGTH,
    INDEX_LENGTH,
    DATA_FREE
from 
    information_schema.tables 
where 
    DATA_FREE is not null 
ORDER BY DATA_FREE DESC LIMIT 30;

SELECT
 t1.table_schema,
 t1.table_name,
 t1.table_type 
FROM
 information_schema.TABLES t1
 LEFT OUTER JOIN information_schema.TABLE_CONSTRAINTS t2 ON t1.table_schema = t2.TABLE_SCHEMA 
 AND t1.table_name = t2.TABLE_NAME 
 AND t2.CONSTRAINT_NAME IN ( 'PRIMARY' ) 
WHERE
 t2.table_name IS NULL 
 AND t1.TABLE_SCHEMA NOT IN ( 'information_schema', 'performance_schema', 'test', 'mysql', 'sys' ) 
 AND t1.table_type = "BASE TABLE";

#主从状态
show slave status\G

#主从是否延迟
Master_Log_File == Relay_Master_Log_File 
&& Read_Master_Log_Pos == Exec_Master_Log_Pos