openGauss每日一练第9天|学习心得

第九天的学习内容主要是进一步学习表空间与数据库对象的关系，了解oid的含义。

一、练习环境

实训环境

二、练习内容及课程作业

我们将通过今天学习的内容完成今天的作业，在开始作业之前，首先要建立测试环境，即创建表空间、多个数据库和用户

su - omm
gsql -r
--进入数据库omm，创建表空间、测试数据库
drop DATABASE  IF EXISTS  musicdb;
drop DATABASE  IF EXISTS  musicdb1;
drop DATABASE  IF EXISTS  musicdb2;
drop DATABASE  IF EXISTS  musicdb3;
drop tablespace IF EXISTS music_tbs;
drop tablespace IF EXISTS ds_location1;


CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb1 WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb2 WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb3 WITH TABLESPACE = music_tbs;

--执行下面的SQL语句，创建用户user1 ：
drop user  IF EXISTS  user1;

CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
  
--授予user1数据库系统的SYSADMIN权限：

ALTER USER user1 SYSADMIN；

结果如下：

root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# drop DATABASE  IF EXISTS  musicdb;
NOTICE:  database "musicdb" does not exist, skipping
omm=# DROP DATABASE
drop DATABASE  IF EXISTS  musicdb1;
NOTICE:  database "musicdb1" does not exist, skipping
DROP DATABASE
omm=# drop DATABASE  IF EXISTS  musicdb2;
NOTICE:  database "musicdb2" does not exist, skipping
DROP DATABASE
omm=# drop DATABASE  IF EXISTS  musicdb3;
DROP DATABASE
omm=# NOTICE:  database "musicdb3" does not exist, skipping
drop tablespace IF EXISTS music_tbs;
NOTICE:  Tablespace "music_tbs" does not exist, skipping.
DROP TABLESPACE
omm=# drop tablespace IF EXISTS ds_location1;
NOTICE:  Tablespace "ds_location1" does not exist, skipping.
DROP TABLESPACE
omm=# 
omm=# 
omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;

CREATE DATABASE
omm=# CREATE DATABASE musicdb1 WITH TABLESPACE = music_tbs;
omm=# CREATE DATABASE musicdb2 WITH TABLESPACE = music_tbs;
CREATE DATABASE

CREATE DATABASE
omm=# CREATE DATABASE musicdb3 WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# 
omm=# drop user  IF EXISTS  user1;
NOTICE:  role "user1" does not exist, skipping
omm=# DROP ROLE

omm=# CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# omm=# ALTER USER user1 SYSADMIN；

1.创建表空间newtbs1

要完成以上操作，只需要执行以下的sql命令即可。

CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/newtbs1';

结果如下：

omm=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/newtbs1';
CREATE TABLESPACE
omm=# 

2.创建3个数据库newdb1、newdb2、newdb3，默认表空间为newtbs1

要完成以上操作，只需要执行以下的sql命令即可。

CREATE DATABASE newdb1 WITH TABLESPACE = newtbs1;
CREATE DATABASE newdb2 WITH TABLESPACE = newtbs1;
CREATE DATABASE newdb3 WITH TABLESPACE = newtbs1;

结果如下：

omm=# CREATE DATABASE newdb1 WITH TABLESPACE = newtbs1;

CREATE DATABASE
omm=# CREATE DATABASE newdb2 WITH TABLESPACE = newtbs1;
CREATE DATABASE
omm=# CREATE DATABASE newdb3 WITH TABLESPACE = newtbs1;
CREATE DATABASE
omm=#

3.使用sql查看表空间newtbs1上有几个数据库

要完成以上操作，只需要执行以下的sql命令即可。

 select oid,datname from pg_database;

select oid,* from pg_tablespace ;

select datname,dattablespace,spcname from pg_database d, pg_tablespace t where d.dattablespace=t.oid; 

结果如下：

omm=# select oid,datname from pg_database;
  oid  |  datname  
-------+-----------
     1 | template1
 16384 | omm
 16390 | musicdb
 14555 | template0
 16391 | musicdb1
 16392 | musicdb2
 16393 | musicdb3
 14560 | postgres
 16399 | newdb1
 16400 | newdb2
 16401 | newdb3
(11 rows)

omm=# select oid,* from pg_tablespace ;
  oid  |  spcname   | spcowner | spcacl | spcoptions | spcmaxsize | relative 
-------+------------+----------+--------+------------+------------+----------
  1663 | pg_default |       10 |        |            |            | f
  1664 | pg_global  |       10 |        |            |            | f
 16389 | music_tbs  |       10 |        |            |            | t
 16398 | newtbs1    |       10 |        |            |            | t
(4 rows)

omm=# select datname,dattablespace,spcname from pg_database d, pg_tablespace t where d.dattablespace=t.oid; 
  datname  | dattablespace |  spcname   
-----------+---------------+------------
 template1 |          1663 | pg_default
 omm       |          1663 | pg_default
 musicdb   |         16389 | music_tbs
 template0 |          1663 | pg_default
 musicdb1  |         16389 | music_tbs
 musicdb2  |         16389 | music_tbs
 musicdb3  |         16389 | music_tbs
 postgres  |          1663 | pg_default
 newdb1    |         16398 | newtbs1
 newdb2    |         16398 | newtbs1
 newdb3    |         16398 | newtbs1
(11 rows)

omm=# 

可以看到newtbs1有3个数据库

4.在文件系统中查看表空间newtbs1中的多个数据库

要完成以上操作，只需要执行以下的sql命令即可。由第3个课后作业，可以知道newtbs1的oid是16398,它下面共有3个数据库，oid分别是16399 16400 16401。

--从文件系统，查看music_tbs表空间oid，可以看到一个表空间可以有多个数据库
 
cd /var/lib/opengauss/data/pg_tblspc/16398/
cd  PG_9.2* 
ls
 #说明：xxxxx是表空间 music_tbs的oid

结果如下：

omm=# cd /var/lib/opengauss/data/pg_tblspc/16398/omm@modb:/var/lib/opengauss/data/pg_tblspc/16398$ cd  PG_9.2* 
omm@modb:/var/lib/opengauss/data/pg_tblspc/16398/PG_9.2_201611171_gaussdb$ ls
16399  16400  16401  pgsql_tmp

三、总结