我们刚刚将数据库从mariadb 5.5.56升级到了MySQL8。我们面临一个问题，即对InnoDB进行某些更新查询需要随机。请注意，在99％的时间内，查询速度很快，但随后突然突然花费大量时间，然后又恢复正常。我们不会在mariadb 5.5.56中遇到此问题
CREATE TABLE `users` (
`uid` int(10) unsigned NOT NULL AUTO_INCREMENT,
`pid` int(10) unsigned NOT NULL DEFAULT '0',
`ipaddr` int(10) unsigned DEFAULT '0',
PRIMARY KEY (`uid`,`pid`),
KEY `pid` (`pid`)
) ENGINE=InnoDB AUTO_INCREMENT=161089 DEFAULT CHARSET=utf8
/*!50100 PARTITION BY HASH (`pid`)
PARTITIONS 101
mysql> update users set ipaddr=2148888835 where uid=1 limit 1;
Query OK, 1 row affected **(39.51 sec)**
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update users set ipaddr=2148888835 where uid=1 limit 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
查询非常简单，它使用如下所示的主键
mysql> explain update users set ipaddr=123 where uid=1;
+----+-------------+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------+---------------+---------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------+---------------+---------+---------+-------+------+----------+-------------+
| 1 | UPDATE | users | p0,p1,p2,p3,p4,p5,p6,p7,p8,p9,p10,p11,p12,p13,p14,p15,p16,p17,p18,p19,p20,p21,p22,p23,p24,p25,p26,p27,p28,p29,p30,p31,p32,p33,p34,p35,p36,p37,p38,p39,p40,p41,p42,p43,p44,p45,p46,p47,p48,p49,p50,p51,p52,p53,p54,p55,p56,p57,p58,p59,p60,p61,p62,p63,p64,p65,p66,p67,p68,p69,p70,p71,p72,p73,p74,p75,p76,p77,p78,p79,p80,p81,p82,p83,p84,p85,p86,p87,p88,p89,p90,p91,p92,p93,p94,p95,p96,p97,p98,p99,p100 | range | PRIMARY | PRIMARY | 4 | const | 1 | 100.00 | Using where |
+----+-------------+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------+---------------+---------+---------+-------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
我启用了性能分析，它显示更新需要很长时间。
mysql> SHOW PROFILE; +--------------------------------+-----------+
| Status | Duration |
+--------------------------------+-----------+
| starting | 0.000045 |
| Executing hook on transaction | 0.000005 |
| starting | 0.000005 |
| checking permissions | 0.000004 |
| Opening tables | 0.000017 |
| init | 0.000005 |
| System lock | 0.000193 |
| updating | 39.470708 |
| end | 0.000009 |
| query end | 0.000004 |
| waiting for handler commit | 0.038291 |
| closing tables | 0.000039 |
| freeing items | 0.000024 |
| cleaning up | 0.000028 |
+--------------------------------+-----------+
14 rows in set, 1 warning (0.00 sec)
尽管这些表是使用mysqldump全新创建的，但我什至尝试优化该表，但这无济于事。
mysql> optimize table users;
+--------------+----------+----------+-------------------------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+--------------+----------+----------+-------------------------------------------------------------------+
| mesibo.users | optimize | note | Table does not support optimize, doing recreate + analyze instead |
| mesibo.users | optimize | status | OK |
+--------------+----------+----------+-------------------------------------------------------------------+
2 rows in set (2 min 3.07 sec)
下面是配置文件。我们的服务器有64GB内存，我们为innodb分配了16G，但是更改此值或从配置中删除它并没有帮助。
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysql/mysqld.log
pid-file=/run/mysqld/mysqld.pid
innodb_buffer_pool_size=16G
max_connections = 1024
任何线索，这里可能有什么问题吗？