mysql中已经存在某个库中有大小写的表,将lower_case_table_names由0改为1对已经存在的表是否有影响?

Posted 2020-11-11 QA-3K

需求描述:

　　今天遇到了修改lower_case_table_names参数的问题,想了下,如果原来里面有表,表名有大小写的,

　　如果将lower_case_table_names从默认的0改为1之后,那么对于原来的表有没有影响.做个实验,在此

　　记录下.

操作过程:

1.原来未修改之前,库中创建大小写区分的表

mysql> drop database test05;
Query OK, 2 rows affected (0.05 sec)

mysql> create database test05;
Query OK, 1 row affected (0.00 sec)

mysql> use test05;
Database changed
mysql> create table tab01(id int); #创建小写的表名
Query OK, 0 rows affected (0.05 sec)

mysql> create table Tab01(id int); #创建大写的表名
Query OK, 0 rows affected (0.04 sec)

mysql> insert into tab01 select 1; #分别向两个表中插入数据
Query OK, 1 row affected (0.01 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into tab01 select 2;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into tab01 select 3;
Query OK, 1 row affected (0.01 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into tab01 select 4;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select 4;
Query OK, 1 row affected (0.01 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select 5;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select 6;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> select * from tab01; #小写表名中的数据
+------+
| id   |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
+------+
4 rows in set (0.00 sec)

mysql> select * from Tab01; #大写表名中的数据
+------+
| id   |
+------+
|    4 |
|    5 |
|    6 |
+------+
3 rows in set (0.00 sec)

2.将lower_case_table_name参数修改为1,重启实例

mysql> select * from Tab01; #查询大写表名,发现是小写表的数据
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    2
Current database: test05

+------+
| id   |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
+------+
4 rows in set (0.01 sec)

mysql> select * from tab01; #查询小写表名,还是小写表的数据
+------+
| id   |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
+------+
4 rows in set (0.00 sec)

mysql> system ls -l /mysql/data/test05  #操作系统上大小写文件都是存在的.
total 220
-rw-r----- 1 mysql mysql    61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql  8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql  8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 98304 Jun  5 17:04 tab01.ibd
-rw-r----- 1 mysql mysql 98304 Jun  5 17:05 Tab01.ibd
mysql> insert into Tab01 select * from tab01;  #继续向大写表名中插数据.
Query OK, 4 rows affected (0.05 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> system ls -l /mysql/data/test05
total 220
-rw-r----- 1 mysql mysql    61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql  8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql  8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 98304 Jun  5 17:07 tab01.ibd
-rw-r----- 1 mysql mysql 98304 Jun  5 17:05 Tab01.ibd
mysql> insert into Tab01 select * from tab01;
Query OK, 8 rows affected (0.01 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql> system ls -l /mysql/data/test05
total 220
-rw-r----- 1 mysql mysql    61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql  8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql  8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 98304 Jun  5 17:07 tab01.ibd  
-rw-r----- 1 mysql mysql 98304 Jun  5 17:05 Tab01.ibd
mysql> insert into Tab01 select * from tab01;
Query OK, 16 rows affected (0.00 sec)
Records: 16  Duplicates: 0  Warnings: 0

mysql> system ls -l /mysql/data/test05
total 220
-rw-r----- 1 mysql mysql    61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql  8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql  8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 98304 Jun  5 17:07 tab01.ibd
-rw-r----- 1 mysql mysql 98304 Jun  5 17:05 Tab01.ibd
mysql> insert into Tab01 select * from tab01;
Query OK, 32 rows affected (0.01 sec)
Records: 32  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select * from tab01;
Query OK, 64 rows affected (0.01 sec)
Records: 64  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select * from tab01;
Query OK, 128 rows affected (0.02 sec)
Records: 128  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select * from tab01;
Query OK, 256 rows affected (0.00 sec)
Records: 256  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select * from tab01;
Query OK, 512 rows affected (0.02 sec)
Records: 512  Duplicates: 0  Warnings: 0

mysql> insert into Tab01 select * from tab01;
Query OK, 1024 rows affected (0.03 sec)
Records: 1024  Duplicates: 0  Warnings: 0

mysql> system ls -l /mysql/data/test05
total 288
-rw-r----- 1 mysql mysql     61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql   8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql   8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 163840 Jun  5 17:08 tab01.ibd  #插入多次发现,只有小写表名的文件大小在变化.
-rw-r----- 1 mysql mysql  98304 Jun  5 17:05 Tab01.ibd
mysql> system ls -l /mysql/data/test05
total 288
-rw-r----- 1 mysql mysql     61 Jun  5 17:03 db.opt
-rw-r----- 1 mysql mysql   8556 Jun  5 17:03 tab01.frm
-rw-r----- 1 mysql mysql   8556 Jun  5 17:04 Tab01.frm
-rw-r----- 1 mysql mysql 163840 Jun  5 17:08 tab01.ibd
-rw-r----- 1 mysql mysql  98304 Jun  5 17:05 Tab01.ibd

 

备注:发现将lower_case_table_names参数从默认的0改为1之后,对于原来表的使用是有影响的,查询的也只是查询小写的表,插入也只是插入到小写的表中,虽然通过show tables能够看到大小写的表同时存在.

 

文档创建时间:2018年6月5日17:20:23