openGauss每日一练第8天 | 信创之路

学习目标

学习表空间与数据库对象的关系。
在musicdb数据库中创建的所有的表，没有指定表空间的名字，因此都创建在数据库默认的表空间music_tbs中，当我们在musicdb数据库中创建表warehouse_t1的时候，明确指定在表空间ds_location1中创建时，这个表会存储在这个指定的表空间。即一个数据库中的对象，可以位于不同的表空间.

课程学习

1.连接数据库，准备测试环境

#第一次进入等待15秒
#数据库启动中...
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;

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

--执行下面的SQL语句，创建用户user1：

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

ALTER USER user1 SYSADMIN;

2.创建表空间、查看表空间

--执行下面的命令，查看当前表空间：
\db
 
--创建一个新的名为ds_location1的表空间：
 
 CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/tablespace_1';
 
--执行下面的命令，查看实例当前有哪些表空间：
\db

3.使用user1用户，访问musicdb数据库 ，在表空间ds_location1上创建表warehouse_t1:

\c musicdb user1

 create table warehouse_t1 (col1 char(10)) tablespace ds_location1;

4.查看musicdb数据库目前有哪些表：

select table_catalog, table_schema, table_name, table_type
  from information_schema.tables
   where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');

1. 查询表在那个表空间
   系统表在默认表空间，非系统表在指定的表空间中（否则在默认表空间）

--建表warehouse_t1指定表空间ds_location1，查看表warehouse_t1所在的表空间：
select * from pg_tables where tablename = 'warehouse_t1';

--创建表warehouse_t12未指定表空间，则在默认表空间（不显示默认表空间名）
create table warehouse_t12 (col1 char(10));
select * from pg_tables where tablename = 'warehouse_t12';

6.查看openGuass数据库的默认表空间

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

7.查询数据库的默认表空间上的对象

select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,relowner  
from pg_class a  
where a.relkind in ('r', 'i')  
and reltablespace='0'  
order by a.relpages desc;

8.查询表空间ds_location1上的对像

\c musicdb user1
select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,relowner  
from pg_class a, pg_tablespace tb  
where a.relkind in ('r', 'i')  
and a.reltablespace=tb.oid  
and tb.spcname='ds_location1'  
order by a.relpages desc;

课后作业

1.创建表空间newtbs1、 ds_location1，查看表空间

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=# 
omm=# 
omm=# 
omm=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/newtbs1';
CREATE TABLESPACE
omm=#  CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/tablespace_1';
CREATE TABLESPACE
omm=# \db
              List of tablespaces
     Name     | Owner |        Location         
--------------+-------+-------------------------
 ds_location1 | omm   | tablespace/tablespace_1
omm=#  music_tbs    | omm   | tablespace/test_ts1
 newtbs1      | omm   | tablespace/newtbs1
 pg_default   | omm   | 
 pg_global    | omm   | 
(5 rows)

2.创建一个数据库newdb1，默认表空间为newtbs1

omm=# CREATE DATABASE newdb1  WITH TABLESPACE = newtbs1;
CREATE DATABASE

3.创建用户user5，并授予SYSADMIN权限，访问数据库newdb1，在表空间ds_location1上，创建一个表newt1（表结构自定义）

omm=#  CREATE USER user5 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user5 SYSADMIN;
ALTER ROLE
omm=# \c newdb1 user5
Password for user user5: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "newdb1" as user "user5".
newdb1=>  create table newt1 (col1 char(10)) tablespace ds_location1;
CREATE TABLE

4.查看表所在的表空间

select * from pg_tables where tablename = 'newt1';
+08 | 2022-12-01 23:45:25.13701+08
(1 row)

 schemaname | tablename | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablecreator |           created        
    |        last_ddl_time         
------------+-----------+------------+--------------+------------+----------+-------------+--------------+--------------------------
----+------------------------------
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5        | 2022-12-01 23:45:25.13701
newdb1=> 

5.查看表空间newtbs1、 ds_location1上的对象

newdb1=> select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,relowner  
newdb1-> from pg_class a, pg_tablespace tb  
newdb1-> where a.relkind in ('r', 'i')  
newdb1-> and a.reltablespace=tb.oid  
newdb1-> and tb.spcname in ('ds_location1' ,'newtbs1' )
newdb1-> order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 newt1   | r       |        0 | 0 bytes        |         16417 |    16419
(1 row)