openGauss每日一练第8天 | 学习心得体会

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.

课后作业

测试环境搭建(创建表空间、测试数据库；创建用户user1，授予数据库系统的SYSADMIN权限)：

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=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=# 

1.创建表空间newtbs1、 ds_location1，查看表空间

【注意：创建表空间时：tablespace/tablespace_1 不可相同，不然会出现路径冲突错误。
如：omm=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/tablespace_1';
ERROR:  find conflict linkpath in pg_tblspc, try a different path.】

操作如下:
omm=# CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/tablespace_1';
CREATE TABLESPACE
omm=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/newtbs1_1';
CREATE TABLESPACE
omm=# \db
              List of tablespaces
     Name     | Owner |        Location         
--------------+-------+-------------------------
 ds_location1 | omm   | tablespace/tablespace_1
 music_tbs    | omm   | tablespace/test_ts1
 newtbs1      | omm   | tablespace/newtbs1_1
 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）

在omm下执行：

omm=# create USER user5 identified by 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
omm=# CREATE ROLE

omm=# alter USER user5 SYSADMIN;
omm=# 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 (col11 char(10)) tablespace ds_location1;
CREATE TABLE

4.查看表所在的表空间

newdb1=> select * from pg_tables where tablename = 'newt1';
 schemaname | tablename | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablecreator |
            created            |         last_ddl_time         
------------+-----------+------------+--------------+------------+----------+-------------+--------------+
-------------------------------+-------------------------------
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5        |
 2022-12-01 17:23:02.170418+08 | 2022-12-01 17:23:02.170418+08
(1 row)

newdb1=> 

5.查看表空间newtbs1、 ds_location1上的对象

omm=# \c musicdb user1
Password for user user1: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "user1".
musicdb=> 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;
   relname    | relkind | relpages | pg_size_pretty | reltablespace | relowner 
--------------+---------+----------+----------------+---------------+----------
 warehouse_t1 | r       |        0 | 0 bytes        |         16395 |    16391
(1 row)

musicdb=> 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='newtbs1'  order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 newdb1  | r       |        0 | 0 bytes        |         16396 |    16391
(1 row)

musicdb=>