技术分享 | 一些 MySQL DBA 实用 SQL 语句
来源：SegmentFault
时间：2023-02-16 19:37:17 452浏览 收藏
亲爱的编程学习爱好者，如果你点开了这篇文章，说明你对《技术分享 | 一些 MySQL DBA 实用 SQL 语句》很感兴趣。本篇文章就来给大家详细解析一下，主要介绍一下MySQL、数据库、DBA，希望所有认真读完的童鞋们，都有实质性的提高。
本文目录：
- 一、连接相关
- 二、长事务
- 三、元数据锁
- 四、锁等待
- 五、全局读锁
- 六、内存使用监控
- 七、分区表
- 八、数据库信息概览
- 九、长时间未更新的表
- 十、主键、索引
- 十一、存储引擎
- 十二、实时负载
阅读提示：
1）本篇文章涉及到大量 SQL 语句，在 PC 端阅读效果更佳。
2）SQL 基于 Oracle MySQL 5.7 版本，其它版本因数据源不同不完全适用。
3）SQL 使用场景包含会话连接、元数据锁、全局锁、锁等待、长事务、内存监控、分区表、低频更新表、主键、索引、存储引擎、实时负载属于工具型文章，建议收藏保存以便后续查看。
一、连接相关
查看某用户连接的会话级别参数设置及状态变量，用于观测其它会话连接行为，辅助定位连接类问题
- 例：查看用户连接 ID 为 19 的字符集设置，也可不指定 PROCESSLIST_ID 条件，查看所有用户连接
SELECT T1.VARIABLE_NAME,
T1.VARIABLE_VALUE,
T2.PROCESSLIST_ID,
concat(T2.PROCESSLIST_USER,"@",T2.PROCESSLIST_HOST),
T2.PROCESSLIST_DB,
T2.PROCESSLIST_COMMAND
FROM PERFORMANCE_SCHEMA.VARIABLES_BY_THREAD T1,
PERFORMANCE_SCHEMA.THREADS T2
WHERE T1.THREAD_ID = T2.THREAD_ID
AND T1.VARIABLE_NAME LIKE 'character%'
AND PROCESSLIST_ID ='19';
+--------------------------+----------------+----------------+-----------------------------------------------------+----------------+---------------------+
| VARIABLE_NAME | VARIABLE_VALUE | PROCESSLIST_ID | concat(T2.PROCESSLIST_USER,"@",T2.PROCESSLIST_HOST) | PROCESSLIST_DB | PROCESSLIST_COMMAND |
+--------------------------+----------------+----------------+-----------------------------------------------------+----------------+---------------------+
| character_set_client | gbk | 19 | root@localhost | db | Query |
| character_set_connection | gbk | 19 | root@localhost | db | Query |
| character_set_database | utf8mb4 | 19 | root@localhost | db | Query |
| character_set_filesystem | binary | 19 | root@localhost | db | Query |
| character_set_results | gbk | 19 | root@localhost | db | Query |
| character_set_server | utf8mb4 | 19 | root@localhost | db | Query |
+--------------------------+----------------+----------------+-----------------------------------------------------+----------------+---------------------+
6 rows in set (0.01 sec)
- 例：发现用户 ID 为 254 的连接关闭了 sql_log_bin 设置
SELECT T1.VARIABLE_NAME,
T1.VARIABLE_VALUE,
T2.PROCESSLIST_ID,
concat(T2.PROCESSLIST_USER,"@",T2.PROCESSLIST_HOST) AS 'User@Host',
T2.PROCESSLIST_DB,
T2.PROCESSLIST_COMMAND
FROM PERFORMANCE_SCHEMA.VARIABLES_BY_THREAD T1,
PERFORMANCE_SCHEMA.THREADS T2
WHERE T1.THREAD_ID = T2.THREAD_ID
AND T1.VARIABLE_NAME LIKE 'sql_log_bin';
+---------------+----------------+----------------+------------------+----------------+---------------------+
| VARIABLE_NAME | VARIABLE_VALUE | PROCESSLIST_ID | User@Host | PROCESSLIST_DB | PROCESSLIST_COMMAND |
+---------------+----------------+----------------+------------------+----------------+---------------------+
| sql_log_bin | OFF | 254 | root@localhost | NULL | Sleep |
| sql_log_bin | ON | 256 | root@localhost | NULL | Sleep |
| sql_log_bin | ON | 257 | root@10.211.55.2 | NULL | Sleep |
| sql_log_bin | ON | 258 | root@10.211.55.2 | NULL | Sleep |
| sql_log_bin | ON | 259 | root@localhost | NULL | Query |
| sql_log_bin | ON | 261 | root@localhost | NULL | Sleep |
+---------------+----------------+----------------+------------------+----------------+---------------------+
4 rows in set (0.00 sec)
- 例：查看用户连接 ID 为 24 的网络流量变化
SELECT T1.VARIABLE_NAME,
T1.VARIABLE_VALUE,
T2.PROCESSLIST_ID,
concat(T2.PROCESSLIST_USER,"@",T2.PROCESSLIST_HOST) AS 'User@Host',
T2.PROCESSLIST_DB,
T2.PROCESSLIST_COMMAND
FROM PERFORMANCE_SCHEMA.STATUS_BY_THREAD T1,
PERFORMANCE_SCHEMA.THREADS T2
WHERE T1.THREAD_ID = T2.THREAD_ID
AND T2.PROCESSLIST_USER = 'root'
AND PROCESSLIST_ID= 24
AND VARIABLE_NAME LIKE 'Byte%';
+----------------+----------------+----------------+----------------+----------------+---------------------+
| VARIABLE_NAME | VARIABLE_VALUE | PROCESSLIST_ID | User@Host | PROCESSLIST_DB | PROCESSLIST_COMMAND |
+----------------+----------------+----------------+----------------+----------------+---------------------+
| Bytes_received | 224 | 24 | root@127.0.0.1 | NULL | Sleep |
| Bytes_sent | 182 | 24 | root@127.0.0.1 | NULL | Sleep |
+----------------+----------------+----------------+----------------+----------------+---------------------+
2 rows in set (0.00 sec)
二、长事务
事务开启后，超过 5s 未提交的用户连接
SELECT trx_mysql_thread_id AS PROCESSLIST_ID,
NOW(),
TRX_STARTED,
TO_SECONDS(now())-TO_SECONDS(trx_started) AS TRX_LAST_TIME ,
USER,
HOST,
DB,
TRX_QUERY
FROM INFORMATION_SCHEMA.INNODB_TRX trx
JOIN INFORMATION_SCHEMA.processlist pcl ON trx.trx_mysql_thread_id=pcl.id
WHERE trx_mysql_thread_id != connection_id()
AND TO_SECONDS(now())-TO_SECONDS(trx_started) >= 5 ;
+----------------+---------------------+---------------------+---------------+------+-----------------+------+-----------+
| PROCESSLIST_ID | NOW() | TRX_STARTED | TRX_LAST_TIME | User | Host | DB | TRX_QUERY |
+----------------+---------------------+---------------------+---------------+------+-----------------+------+-----------+
| 24 | 2019-12-16 02:49:52 | 2019-12-16 02:41:15 | 517 | root | 127.0.0.1:58682 | db | NULL |
+----------------+---------------------+---------------------+---------------+------+-----------------+------+-----------+
1 row in set (0.01 sec)
三、元数据锁
MySQL 5.7 开启元数据锁追踪，以便追踪定位元数据锁相关的阻塞问题
// 临时开启，动态生效 UPDATE performance_schema.setup_consumers SET ENABLED = 'YES' WHERE NAME ='global_instrumentation'; UPDATE performance_schema.setup_instruments SET ENABLED = 'YES' WHERE NAME ='wait/lock/metadata/sql/mdl'; // 配置文件中添加，重启生效 performance-schema-instrument = wait/lock/metadata/sql/mdl=ON
场景 1：杀掉持有 MDL 锁的会话，使 DDL 语句顺利执行。
- DDL 语句被阻塞通常因为存在获取资源后未及时提交释放的长事务。因此，查找 kill 掉事务运行时间大于 DDL 运行时间的会话即可使 DDL 语句顺利下发，SQL 语句如下：
// 查找事务运行时间 >= DDL等待时间的线程
SELECT trx_mysql_thread_id AS PROCESSLIST_ID,
NOW(),
TRX_STARTED,
TO_SECONDS(now())-TO_SECONDS(trx_started) AS TRX_LAST_TIME ,
USER,
HOST,
DB,
TRX_QUERY
FROM INFORMATION_SCHEMA.INNODB_TRX trx
JOIN INFORMATION_SCHEMA.processlist pcl ON trx.trx_mysql_thread_id=pcl.id
WHERE trx_mysql_thread_id != connection_id()
AND TO_SECONDS(now())-TO_SECONDS(trx_started) >=
(SELECT MAX(Time)
FROM INFORMATION_SCHEMA.processlist
WHERE STATE='Waiting for table metadata lock'
AND INFO LIKE 'alter%table%' OR INFO LIKE 'truncate%table%') ;
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
| PROCESSLIST_ID | NOW() | TRX_STARTED | TRX_LAST_TIME | User | Host | DB | TRX_QUERY |
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
| 253 | 2019-12-24 01:42:11 | 2019-12-24 01:41:24 | 47 | root | localhost | NULL | NULL |
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
1 row in set (0.00 sec)
// kill掉长事务，释放持有的MDL资源
kill 253;
注：因 MySQL 元数据信息记录有限，此处可能误杀无辜长事务，且误杀无法完全避免。
- 当 kill 掉阻塞源后，可能存在 DDL 语句与被阻塞的 SQL 语句同时加锁的情况，此时会出现事务开始时间等于 DDL 开始时间连接，此类事务也需 kill。
//查找事务开始时间 = DDL语句事务开始时间的线程
SELECT trx_mysql_thread_id AS PROCESSLIST_ID,
NOW(),
TRX_STARTED,
TO_SECONDS(now())-TO_SECONDS(trx_started) AS TRX_LAST_TIME ,
USER,
HOST,
DB,
TRX_QUERY
FROM INFORMATION_SCHEMA.INNODB_TRX trx
JOIN INFORMATION_SCHEMA.processlist pcl ON trx.trx_mysql_thread_id=pcl.id
WHERE trx_mysql_thread_id != connection_id()
AND trx_started =
(SELECT MIN(trx_started)
FROM INFORMATION_SCHEMA.INNODB_TRX
GROUP BY trx_started HAVING count(trx_started)>=2)
AND TRX_QUERY NOT LIKE 'alter%table%'
OR TRX_QUERY IS NULL;
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
| PROCESSLIST_ID | NOW() | TRX_STARTED | TRX_LAST_TIME | User | Host | DB | TRX_QUERY |
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
| 255 | 2019-12-24 01:42:44 | 2019-12-24 01:42:33 | 11 | root | localhost | NULL | NULL |
+----------------+---------------------+---------------------+---------------+------+-----------+------+-----------+
1 row in set (0.00 sec)
//杀掉阻塞源
kill 255;
场景 2：kill 掉下发 DDL 语句的用户连接，取消 DDL 语句下发，保障业务不被阻塞。
// 查找DDL语句所在用户连接 SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST WHERE INFO LIKE 'ALTER%TABLE%'; +-----+------+-----------+------+---------+------+---------------------------------+----------------------------------+ | ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | +-----+------+-----------+------+---------+------+---------------------------------+----------------------------------+ | 254 | root | localhost | NULL | Query | 730 | Waiting for table metadata lock | alter table db.t1 add index (id) | +-----+------+-----------+------+---------+------+---------------------------------+----------------------------------+ 1 row in set (0.00 sec) // 杀掉DDL语句所在用户连接 kill 254;
四、锁等待
查看锁等待相关的阻塞线程、被阻塞线程信息及相关用户、IP、PORT
SELECT locked_table,
locked_index,
locked_type,
blocking_pid,
concat(T2.USER,'@',T2.HOST) AS "blocking(user@ip:port)",
blocking_lock_mode,
blocking_trx_rows_modified,
waiting_pid,
concat(T3.USER,'@',T3.HOST) AS "waiting(user@ip:port)",
waiting_lock_mode,
waiting_trx_rows_modified,
wait_age_secs,
waiting_query
FROM sys.x$innodb_lock_waits T1
LEFT JOIN INFORMATION_SCHEMA.processlist T2 ON T1.blocking_pid=T2.ID
LEFT JOIN INFORMATION_SCHEMA.processlist T3 ON T3.ID=T1.waiting_pid;
+--------------+--------------+-------------+--------------+------------------------+--------------------+----------------------------+-------------+-----------------------+-------------------+---------------------------+---------------+---------------------------------+
| locked_table | locked_index | locked_type | blocking_pid | blocking(user@ip:port) | blocking_lock_mode | blocking_trx_rows_modified | waiting_pid | waiting(user@ip:port) | waiting_lock_mode | waiting_trx_rows_modified | wait_age_secs | waiting_query |
+--------------+--------------+-------------+--------------+------------------------+--------------------+----------------------------+-------------+-----------------------+-------------------+---------------------------+---------------+---------------------------------+
| `db`.`t1` | PRIMARY | RECORD | 228 | dks@127.0.0.1:56724 | X | 1 | 231 | root@127.0.0.1:50852 | S | 0 | 1 | insert into db.t1(id) values(2) |
+--------------+--------------+-------------+--------------+------------------------+--------------------+----------------------------+-------------+-----------------------+-------------------+---------------------------+---------------+---------------------------------+
1 row in set, 3 warnings (0.00 sec)
- 若不关心阻塞相关的用户、IP、PORT，可直接查看 innodb_lock_waits 表信息。
select * from sys.x$innodb_lock_waits\G
*************************** 1. row ***************************
wait_started: 2019-12-23 02:14:22
wait_age: 00:00:32
wait_age_secs: 32
locked_table: `db`.`t1`
locked_index: PRIMARY
locked_type: RECORD
waiting_trx_id: 7204404
waiting_trx_started: 2019-12-23 02:14:18
waiting_trx_age: 00:00:36
waiting_trx_rows_locked: 1
waiting_trx_rows_modified: 0
waiting_pid: 213
waiting_query: delete from db.t1 where id=200
waiting_lock_id: 7204404:1994:3:4
waiting_lock_mode: X
blocking_trx_id: 7204394
blocking_pid: 207
blocking_query: select * from sys.x$innodb_lock_waits
blocking_lock_id: 7204394:1994:3:4
blocking_lock_mode: X
blocking_trx_started: 2019-12-23 02:10:06
blocking_trx_age: 00:04:48
blocking_trx_rows_locked: 1
blocking_trx_rows_modified: 1
sql_kill_blocking_query: KILL QUERY 207
sql_kill_blocking_connection: KILL 207
1 row in set, 3 warnings (0.00 sec)
影响锁等待超时的参数
五、全局读锁
PERFORMANCE_SCHEMA.METADATA_LOCKS 表 LOCK_DURATION 列为 EXPLICIT 状态表示 FTWRL 语句添加，OBJECT_TYPE 出现 COMMIT 状态表示已经加锁成功
- 场景 1：杀掉添加 FTWRL 的会话，恢复业务运行
SELECT processlist_id,
mdl.OBJECT_TYPE,
OBJECT_SCHEMA,
OBJECT_NAME,
LOCK_TYPE,
LOCK_DURATION,
LOCK_STATUS
FROM performance_schema.metadata_locks mdl
INNER JOIN performance_schema.threads thd ON mdl.owner_thread_id = thd.thread_id
AND processlist_id connection_id()
AND LOCK_DURATION='EXPLICIT';
+----------------+-------------+---------------+-------------+-----------+---------------+-------------+
| processlist_id | OBJECT_TYPE | OBJECT_SCHEMA | OBJECT_NAME | LOCK_TYPE | LOCK_DURATION | LOCK_STATUS |
+----------------+-------------+---------------+-------------+-----------+---------------+-------------+
| 231 | GLOBAL | NULL | NULL | SHARED | EXPLICIT | GRANTED |
| 231 | COMMIT | NULL | NULL | SHARED | EXPLICIT | GRANTED |
+----------------+-------------+---------------+-------------+-----------+---------------+-------------+
2 rows in set (0.00 sec)
// 杀掉添加FTWRL的用户连接
kill 231;
- 场景 2：杀掉语句执行时间大于 FTWRL 执行时间的线程，确保 FTWRL 下发成功
SELECT T2.THREAD_ID,
T1.ID AS PROCESSLIST_ID,
T1.User,
T1.Host,
T1.db,
T1.Time,
T1.State,
T1.Info,
T3.TRX_STARTED,
TO_SECONDS(now())-TO_SECONDS(trx_started) AS TRX_LAST_TIME
FROM INFORMATION_SCHEMA.processlist T1
LEFT JOIN PERFORMANCE_SCHEMA.THREADS T2 ON T1.ID=T2.PROCESSLIST_ID
LEFT JOIN INFORMATION_SCHEMA.INNODB_TRX T3 ON T1.id=T3.trx_mysql_thread_id
WHERE T1.TIME >=
(SELECT MAX(Time)
FROM INFORMATION_SCHEMA.processlist
WHERE INFO LIKE 'flush%table%with%read%lock')
AND Info IS NOT NULL;
+-----------+----------------+------+-------------------+------+------+-------------------------+---------------------------------------------+---------------------+---------------+
| THREAD_ID | PROCESSLIST_ID | User | Host | db | Time | State | Info | TRX_STARTED | TRX_LAST_TIME |
+-----------+----------------+------+-------------------+------+------+-------------------------+---------------------------------------------+---------------------+---------------+
| 284 | 246 | root | localhost | NULL | 364 | User sleep | select * from db.t1 where sleep(1000000000) | 2019-12-23 14:57:23 | 364 |
| 286 | 248 | root | 10.211.55.2:55435 | NULL | 232 | Waiting for table flush | flush table with read lock | NULL | NULL |
+-----------+----------------+------+-------------------+------+------+-------------------------+---------------------------------------------+---------------------+---------------+
2 rows in set (0.00 sec)
六、内存使用监控
默认只对 performance_schema 库进行内存统计，对全局内存统计需要手工开启
//动态开启，开启后开始统计 update performance_schema.setup_instruments set enabled = 'yes' where name like 'memory%'; //配置文件中添加，重启生效 performance-schema-instrument='memory/%=COUNTED'
- 查看实例内存消耗分布，sys 库下有多张 memory 相关视图用于协助用户定位分析内存溢出类问题
SELECT event_name,
current_alloc
FROM sys.memory_global_by_current_bytes
WHERE event_name LIKE 'memory%innodb%';
+-------------------------------------------+---------------+
| event_name | current_alloc |
+-------------------------------------------+---------------+
| memory/innodb/buf_buf_pool | 134.31 MiB |
| memory/innodb/log0log | 32.01 MiB |
| memory/innodb/mem0mem | 15.71 MiB |
| memory/innodb/lock0lock | 12.21 MiB |
| memory/innodb/os0event | 8.37 MiB |
| memory/innodb/hash0hash | 4.74 MiB |
...
+-------------------------------------------+---------------+
42 rows in set (0.01 sec)
七、分区表
- 查看实例中的分区表相关信息
SELECT TABLE_SCHEMA,
TABLE_NAME,
count(PARTITION_NAME) AS PARTITION_COUNT,
sum(TABLE_ROWS) AS TABLE_TOTAL_ROWS,
CONCAT(ROUND(SUM(DATA_LENGTH) / (1024 * 1024), 2),'M') DATA_LENGTH,
CONCAT(ROUND(SUM(INDEX_LENGTH) / (1024 * 1024), 2),'M') INDEX_LENGTH,
CONCAT(ROUND(ROUND(SUM(DATA_LENGTH + INDEX_LENGTH)) / (1024 * 1024),2),'M') TOTAL_SIZE
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_NAME NOT IN ('sys',
'mysql',
'INFORMATION_SCHEMA',
'performance_schema')
AND PARTITION_NAME IS NOT NULL
GROUP BY TABLE_SCHEMA,
TABLE_NAME
ORDER BY sum(DATA_LENGTH + INDEX_LENGTH) DESC ;
+--------------+------------------+-----------------+------------------+-------------+--------------+------------+
| TABLE_SCHEMA | TABLE_NAME | PARTITION_COUNT | TABLE_TOTAL_ROWS | DATA_LENGTH | INDEX_LENGTH | TOTAL_SIZE |
+--------------+------------------+-----------------+------------------+-------------+--------------+------------+
| db | t1 | 365 | 0 | 5.70M | 17.11M | 22.81M |
| db | t2 | 391 | 0 | 6.11M | 0.00M | 6.11M |
| db | t3 | 4 | 32556 | 2.28M | 0.69M | 2.97M |
| db | t4 | 26 | 0 | 0.41M | 2.44M | 2.84M |
| db | t5 | 4 | 0 | 0.06M | 0.00M | 0.06M |
| db | t6 | 4 | 0 | 0.06M | 0.00M | 0.06M |
+--------------+------------------+-----------------+------------------+-------------+--------------+------------+
6 rows in set (1.04 sec)
- 查看某分区表具体信息，此处以库名为 db、表名为 e 的分区表为例
SELECT TABLE_SCHEMA,
TABLE_NAME,
PARTITION_NAME,
PARTITION_EXPRESSION,
PARTITION_METHOD,
PARTITION_DESCRIPTION,
TABLE_ROWS,
CONCAT(ROUND(DATA_LENGTH / (1024 * 1024), 2),'M') DATA_LENGTH,
CONCAT(ROUND(INDEX_LENGTH / (1024 * 1024), 2),'M') INDEX_LENGTH,
CONCAT(ROUND(ROUND(DATA_LENGTH + INDEX_LENGTH) / (1024 * 1024),2),'M') TOTAL_SIZE
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_SCHEMA NOT IN ('sys',
'mysql',
'INFORMATION_SCHEMA',
'performance_schema')
AND PARTITION_NAME IS NOT NULL
AND TABLE_SCHEMA='db'
AND TABLE_NAME='e';
+--------------+------------+----------------+----------------------+------------------+-----------------------+------------+-------------+--------------+------------+
| TABLE_SCHEMA | TABLE_NAME | PARTITION_NAME | PARTITION_EXPRESSION | PARTITION_METHOD | PARTITION_DESCRIPTION | TABLE_ROWS | DATA_LENGTH | INDEX_LENGTH | TOTAL_SIZE |
+--------------+------------+----------------+----------------------+------------------+-----------------------+------------+-------------+--------------+------------+
| db | e | p0 | id | RANGE | 50 | 4096 | 0.20M | 0.09M | 0.30M |
| db | e | p1 | id | RANGE | 100 | 6144 | 0.28M | 0.13M | 0.41M |
| db | e | p2 | id | RANGE | 150 | 6144 | 0.28M | 0.13M | 0.41M |
| db | e | p3 | id | RANGE | MAXVALUE | 16172 | 1.52M | 0.34M | 1.86M |
+--------------+------------+----------------+----------------------+------------------+-----------------------+------------+-------------+--------------+------------+
4 rows in set (0.00 sec)
八、数据库信息概览
- 统计实例中各数据库大小
SELECT TABLE_SCHEMA,
round(SUM(data_length+index_length)/1024/1024,2) AS TOTAL_MB,
round(SUM(data_length)/1024/1024,2) AS DATA_MB,
round(SUM(index_length)/1024/1024,2) AS INDEX_MB,
COUNT(*) AS TABLES
FROM INFORMATION_SCHEMA.tables
WHERE TABLE_SCHEMA NOT IN ('sys',
'mysql',
'INFORMATION_SCHEMA',
'performance_schema')
GROUP BY TABLE_SCHEMA
ORDER BY 2 DESC;
+--------------+----------+---------+----------+--------+
| TABLE_SCHEMA | TOTAL_MB | DATA_MB | INDEX_MB | TABLES |
+--------------+----------+---------+----------+--------+
| cloud | 229.84 | 223.02 | 6.83 | 41 |
| db | 66.42 | 30.56 | 35.86 | 31 |
| dks | 14.41 | 9.70 | 4.70 | 621 |
| test | 0.06 | 0.06 | 0.00 | 4 |
| db2 | 0.03 | 0.03 | 0.00 | 2 |
+--------------+----------+---------+----------+--------+
5 rows in set, 1 warning (0.91 sec)
- 统计某库下各表大小
SELECT TABLE_SCHEMA,
TABLE_NAME TABLE_NAME,
CONCAT(ROUND(data_length / (1024 * 1024), 2),'M') data_length,
CONCAT(ROUND(index_length / (1024 * 1024), 2),'M') index_length,
CONCAT(ROUND(ROUND(data_length + index_length) / (1024 * 1024),2),'M') total_size,
engine
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA NOT IN ('INFORMATION_SCHEMA' ,
'performance_schema',
'sys',
'mysql')
AND TABLE_SCHEMA='db'
ORDER BY (data_length + index_length) DESC LIMIT 10;
+--------------+-----------------------+-------------+--------------+------------+--------+
| TABLE_SCHEMA | table_name | data_length | index_length | total_size | engine |
+--------------+-----------------------+-------------+--------------+------------+--------+
| db | t1 | 5.70M | 22.81M | 28.52M | InnoDB |
| db | t2 | 15.19M | 9.59M | 24.78M | InnoDB |
| db | t3 | 6.11M | 0.00M | 6.11M | InnoDB |
| db | t4 | 2.28M | 0.69M | 2.97M | InnoDB |
| db | t5 | 0.41M | 2.44M | 2.84M | InnoDB |
| db | t6 | 0.17M | 0.00M | 0.17M | InnoDB |
| db | t7 | 0.17M | 0.00M | 0.17M | InnoDB |
| db | t8 | 0.02M | 0.11M | 0.13M | InnoDB |
| db | t9 | 0.08M | 0.00M | 0.08M | InnoDB |
| db | t10 | 0.05M | 0.02M | 0.06M | InnoDB |
+--------------+-----------------------+-------------+--------------+------------+--------+
10 rows in set, 1 warning (0.01 sec)
- 查看某库下表的基本信息
SELECT TABLE_SCHEMA,
TABLE_NAME,
table_collation,
engine,
table_rows
FROM INFORMATION_SCHEMA.tables
WHERE TABLE_SCHEMA NOT IN ('INFORMATION_SCHEMA' ,
'sys',
'mysql',
'performance_schema')
AND TABLE_TYPE='BASE TABLE'
AND TABLE_SCHEMA='db'
ORDER BY table_rows DESC ;
+--------------+-----------------------+--------------------+--------+------------+
| TABLE_SCHEMA | table_name | table_collation | engine | table_rows |
+--------------+-----------------------+--------------------+--------+------------+
| db | t1 | utf8_general_ci | InnoDB | 159432 |
| db | t2 | utf8mb4_general_ci | InnoDB | 32556 |
| db | t3 | utf8mb4_general_ci | InnoDB | 2032 |
...
| db | t100 | utf8mb4_general_ci | InnoDB | 0 |
| db | t101 | utf8mb4_general_ci | InnoDB | 0 |
+--------------+-----------------------+--------------------+--------+------------+
25 rows in set, 1 warning (0.01 sec)
九、长时间未更新的表
UPDATE_TIME 为 NULL 表示实例启动后一直未更新过
SELECT TABLE_SCHEMA,
TABLE_NAME,
UPDATE_TIME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA NOT IN ('SYS',
'MYSQL',
'INFORMATION_SCHEMA',
'PERFORMANCE_SCHEMA')
AND TABLE_TYPE='BASE TABLE'
ORDER BY UPDATE_TIME ;
+--------------+-----------------------+---------------------+
| TABLE_SCHEMA | TABLE_NAME | UPDATE_TIME |
+--------------+-----------------------+---------------------+
| db | t1 | NULL |
| db | t2 | NULL |
| db | t3 | NULL |
| db | t4 | 2019-12-16 07:45:29 |
| db | t5 | 2019-12-16 16:52:01 |
+--------------+-----------------------+---------------------+
22 rows in set, 1 warning (0.01 sec)
十、主键、索引
无主键、唯一键及二级索引基表
- MySQL Innodb 存储引擎为索引组织表，因此设置合适的主键字段对性能至关重要
SELECT T1.TABLE_SCHEMA,
T1.TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS T1 JOIN INFORMATION_SCHEMA.TABLES T2 ON T1.TABLE_SCHEMA=T2.TABLE_SCHEMA AND T1.TABLE_NAME=T2.TABLE_NAME
WHERE T1.TABLE_SCHEMA NOT IN ('SYS',
'MYSQL',
'INFORMATION_SCHEMA',
'PERFORMANCE_SCHEMA')
AND T2.TABLE_TYPE='BASE TABLE'
AND T1.TABLE_SCHEMA='db'
GROUP BY T1.TABLE_SCHEMA,
T1.TABLE_NAME HAVING MAX(COLUMN_KEY)='';
无主键、唯一键，仅有二级索引表
- 该类型表因无高效索引，因此从库回放时容易导致复制延迟
SELECT T1.TABLE_SCHEMA,
T1.TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS T1 JOIN INFORMATION_SCHEMA.TABLES T2 ON T1.TABLE_SCHEMA=T2.TABLE_SCHEMA AND T1.TABLE_NAME=T2.TABLE_NAME
WHERE T1.TABLE_SCHEMA NOT IN ('SYS',
'MYSQL',
'INFORMATION_SCHEMA',
'PERFORMANCE_SCHEMA')
AND T2.TABLE_TYPE='BASE TABLE'
AND T1.COLUMN_KEY != ''
GROUP BY T1.TABLE_SCHEMA,
T1.TABLE_NAME HAVING group_concat(COLUMN_KEY) NOT REGEXP 'PRI|UNI';
仅有主键、唯一键表
- 该类型表结构因无二级索引，可能导致应用 SQL 语句上线后频繁全表扫描出现性能抖动
SELECT T1.TABLE_SCHEMA,
T1.TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS T1 JOIN INFORMATION_SCHEMA.TABLES T2 ON T1.TABLE_SCHEMA=T2.TABLE_SCHEMA AND T1.TABLE_NAME=T2.TABLE_NAME
WHERE T1.TABLE_SCHEMA NOT IN ('SYS',
'MYSQL',
'INFORMATION_SCHEMA',
'PERFORMANCE_SCHEMA')
AND T2.TABLE_TYPE='BASE TABLE'
AND T1.COLUMN_KEY != ''
AND T1.TABLE_SCHEMA='db'
GROUP BY T1.TABLE_SCHEMA,
T1.TABLE_NAME HAVING group_concat(COLUMN_KEY) NOT REGEXP 'MUL';
无主键、唯一键表
SELECT T1.TABLE_SCHEMA,
T1.TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS T1 JOIN INFORMATION_SCHEMA.TABLES T2 ON T1.TABLE_SCHEMA=T2.TABLE_SCHEMA AND T1.TABLE_NAME=T2.TABLE_NAME
WHERE T1.TABLE_SCHEMA NOT IN ('SYS',
'MYSQL',
'INFORMATION_SCHEMA',
'PERFORMANCE_SCHEMA')
AND T2.TABLE_TYPE='BASE TABLE'
GROUP BY T1.TABLE_SCHEMA,
T1.TABLE_NAME HAVING group_concat(COLUMN_KEY) NOT REGEXP 'PRI|UNI';
十一、存储引擎
- 存储引擎分布
SELECT TABLE_SCHEMA,
ENGINE,
COUNT(*)
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA NOT IN ('INFORMATION_SCHEMA' ,
'PERFORMANCE_SCHEMA',
'SYS',
'MYSQL')
AND TABLE_TYPE='BASE TABLE'
GROUP BY TABLE_SCHEMA,
ENGINE;
- 非 INNODB 存储引擎表
SELECT TABLE_SCHEMA,
TABLE_NAME,
TABLE_COLLATION,
ENGINE,
TABLE_ROWS
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA NOT IN ('INFORMATION_SCHEMA' ,
'SYS',
'MYSQL',
'PERFORMANCE_SCHEMA')
AND TABLE_TYPE='BASE TABLE'
AND ENGINE NOT IN ('INNODB')
ORDER BY TABLE_ROWS DESC ;
十二、实时负载
while true
do
mysqladmin -uroot -pxxxxxxx extended-status -r -i 1 -c 30 --socket=/mysqldata/mysqld.sock 2>/dev/null|awk -F"|" "BEGIN{ count=0 ;}"'{ if($2 ~ /Variable_name/ && ++count == 1){\
print "----------|---------|--- MySQL Command Status --|----- Innodb row operation ----|-- Buffer Pool Read --";\
print "---Time---|---QPS---|select insert update delete| read inserted updated deleted| logical physical";\
}\
else if ($2 ~ /Queries/){queries=$3;}\
else if ($2 ~ /Com_select /){com_select=$3;}\
else if ($2 ~ /Com_insert /){com_insert=$3;}\
else if ($2 ~ /Com_update /){com_update=$3;}\
else if ($2 ~ /Com_delete /){com_delete=$3;}\
else if ($2 ~ /Innodb_rows_read/){innodb_rows_read=$3;}\
else if ($2 ~ /Innodb_rows_deleted/){innodb_rows_deleted=$3;}\
else if ($2 ~ /Innodb_rows_inserted/){innodb_rows_inserted=$3;}\
else if ($2 ~ /Innodb_rows_updated/){innodb_rows_updated=$3;}\
else if ($2 ~ /Innodb_buffer_pool_read_requests/){innodb_lor=$3;}\
else if ($2 ~ /Innodb_buffer_pool_reads/){innodb_phr=$3;}\
else if ($2 ~ /Uptime / && count >= 2){\
printf(" %s |%9d",strftime("%H:%M:%S"),queries);\
printf("|%6d %6d %6d %6d",com_select,com_insert,com_update,com_delete);\
printf("|%6d %8d %7d %7d",innodb_rows_read,innodb_rows_inserted,innodb_rows_updated,innodb_rows_deleted);\
printf("|%10d %11d\n",innodb_lor,innodb_phr);\
}}'
done以上就是《技术分享 | 一些 MySQL DBA 实用 SQL 语句》的详细内容，更多关于mysql的资料请关注golang学习网公众号！
声明：本文转载于：SegmentFault 如有侵犯，请联系study_golang@163.com删除
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