openGauss每日一练第8天

今日目标：学习表空间与数据库对象的关系。

系统视图

• pg_tables
  

系统视图

• pg_class

  PG_CLASS系统表存储数据库对象信息及其之间的关系

• PG_TABLESPACE
  PG_TABLESPACE系统表存储表空间信息。
  

1.实验准备

• 创建表空间music_tbs ，并在该表空间下创建数据库musicdb

创建user1，并授予sysadmin权限

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 sysadmin  identified by 'gauss@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# \db
           List of tablespaces
    Name    | Owner |      Location       
------------+-------+---------------------
 music_tbs  | omm   | tablespace/test_ts1
 pg_default | omm   | 
 pg_global  | omm   | 
(3 rows)

omm=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 musicdb   | omm   | UTF8     | C       | C     | 
 omm       | omm   | UTF8     | C       | C     | 
 postgres  | omm   | UTF8     | C       | C     | 
 template0 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
 template1 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
(5 rows)

omm=# \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of 
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

omm=# 

• openGauss的默认表空间查看

musicdb=> 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
 newdb1    |         16396 | newtbs1
 postgres  |          1663 | pg_default
(6 rows)

• 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;
  

2.课后作业

2.1.创建表空间newtbs1、 ds_location1，查看表空间

\db // 查看表表空间

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
 music_tbs    | omm   | tablespace/test_ts1
 pg_default   | omm   | 
 pg_global    | omm   | 
(4 rows)

omm=# create tablespace newtbs1 relative location 'tablespace/newtbs_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/newtbs_1
 pg_default   | omm   | 
 pg_global    | omm   | 
(5 rows)

omm=# 

2.2 创建一个数据库newdb1，默认表空间为newtbs1

omm=# create database newdb1 with tablespace = newtbs1 ;
CREATE DATABASE

2.3 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）

musicdb=> create user user5 sysadmin identified by 'gauss@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
musicdb=> \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=> \db
              List of tablespaces
     Name     | Owner |        Location         
--------------+-------+-------------------------
 ds_location1 | omm   | tablespace/tablespace_1
 music_tbs    | omm   | tablespace/test_ts1
 newtbs1      | omm   | tablespace/newtbs_1
 pg_default   | omm   | 
 pg_global    | omm   | 
(5 rows)

newdb1=> create table newt1(col1 char(50)) tablespace ds_location1 ;
CREATE TABLE
newdb1=>

2.4.查看表所在的表空间

newdb1=> create table newt1(col1 char(50)) tablespace ds_location1 ;
CREATE TABLE
newdb1=> \dt
                         List of relations
 Schema | Name  | Type  | Owner |             Storage              
--------+-------+-------+-------+----------------------------------
 public | newt1 | table | user5 | {orientation=row,compression=no}
(1 row)

newdb1=> select * from pg_tables where tablename = 'newt1';
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5        | 2022-12-01 23:58:31.702802+08 | 2022-1
2-01 23:58:31.702802+08
(1 row)

 schemaname | tablename | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablecreator |            created            |       
  last_ddl_time         
------------+-----------+------------+--------------+------------+----------+-------------+--------------+-------------------------------+-------
------------------------

2.5 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='ds_location1'  
newdb1-> ;                        
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 newt1   | r       |        0 | 0 bytes        |         16395 |    16404
(1 row)

newdb1=> 
newdb1=> 
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='newtbs1' ;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
(0 rows)

newdb1=> \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 musicdb   | omm   | UTF8     | C       | C     | 
 newdb1    | omm   | UTF8     | C       | C     | 
 omm       | omm   | UTF8     | C       | C     | 
 postgres  | omm   | UTF8     | C       | C     | 
 template0 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
 template1 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
(6 rows)

newdb1=>