MySQL:RR模式下insert也可能导致查询慢

来源：这里教程网时间：2026-03-01 15:39:21 作者：

公众号 MySQL学习 
---
RR隔离级别，简单记录如下
#####1、session 1开启read view
```
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> create table testin(id int);
Query OK, 0 rows affected (0.11 sec)
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from testin;
Empty set (0.01 sec)
```
#####2、session 2 不断插入数据
```
mysql> insert into testin select * from testin;
Query OK, 65536 rows affected (14.11 sec)
Records: 65536  Duplicates: 0  Warnings: 0
mysql> select count(*) from testin;
+----------+
| count(*) |
+----------+
|   131072 |
+----------+
1 row in set (6.82 sec)
mysql> insert into testin select * from testin;
Query OK, 131072 rows affected (27.86 sec)
Records: 131072  Duplicates: 0  Warnings: 0
mysql> select count(*) from testin;
+----------+
| count(*) |
+----------+
|   262144 |
+----------+
1 row in set (13.46 sec)
mysql> insert into testin select * from testin;
Query OK, 262144 rows affected (55.49 sec)
Records: 262144  Duplicates: 0  Warnings: 0
```
#####3、session 1查询时间不断递增
```
mysql> select count(*) from testin;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.40 sec)
mysql> select count(*) from testin;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.41 sec)
mysql> select count(*) from testin;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.40 sec)
mysql> select *from testin;
Empty set (0.41 sec)
mysql> select *from testin;
Empty set (0.98 sec)
mysql> select *from testin;
Empty set (2.72 sec)
mysql> select *from testin;
Empty set (2.97 sec)
```
应该是在read view的作用下做了很多跳过处理，当然RC 会直观的观察到数据的变化，但是RR则会在可见性的判断下跳过这些行。
慢查询由于innodb层mysql层没有交互因此看不到扫描了行。但是实际上是做了行扫描的。
```
# Time: 2020-12-16T21:23:34.622196-05:00
# User@Host: root[root] @ localhost []  Id:     7
# Schema: test  Last_errno: 0  Killed: 0
# Query_time: 2.966895  Lock_time: 0.000124  Rows_sent: 0  Rows_examined: 0  Rows_affected: 0
# Bytes_sent: 62
SET timestamp=1608171814;
select *from testin;
```