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首页 / openGauss每日一练第8天 | 学习心得

openGauss每日一练第8天 | 学习心得

原创 建成 2022-12-01
131

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

musicdb=> \db
           List of tablespaces
    Name    | Owner |      Location       
------------+-------+---------------------
 music_tbs  | omm   | tablespace/test_ts1
 pg_default | omm   | 
 pg_global  | omm   | 
(3 rows)
musicdb=> create tablespace ds_location1 relative location 'tablespace/tablespace_1';
CREATE TABLESPACE
musicdb=> \db
(4 rows)

musicdb=>               List of tablespaces
     Name     | Owner |        Location         
--------------+-------+-------------------------
 ds_location1 | user1 | tablespace/tablespace_1
 music_tbs    | omm   | tablespace/test_ts1
 pg_default   | omm   | 
 pg_global    | omm   |


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');

输出如下：

musicdb=> select table_catalog, table_schema, table_name, table_type
musicdb->   from information_schema.tables
musicdb->    where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');
 table_catalog |  table_schema   | table_name  | table_type 
---------------+-----------------+-------------+------------
 musicdb       | db4ai           | snapshot    | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_errors   | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_source   | BASE TABLE
 musicdb       | public          | warehose_t1 | BASE TABLE
(4 rows)
musicdb=>

5.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）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';

结果如下：

musicdb=> select * from pg_tables where tablename='warehose_t1';
 schemaname |  tablename  | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablec
reator |            created            |         last_ddl_time         
------------+-------------+------------+--------------+------------+----------+-------------+-------
-------+-------------------------------+-------------------------------
 public     | warehose_t1 | user1      | ds_location1 | f          | f        | f           | user1 
       | 2022-12-01 20:15:28.656766+08 | 2022-12-01 20:15:28.656766+08
(1 row)
musicdb=> create table warehouse_t12(col1 char(10));
CREATE TABLE
musicdb=> select * from pg_tables where tablename='warehouse_t12';
 schemaname |   tablename   | tableowner | tablespace | hasindexes | hasrules | hastriggers | tablec
reator |            created            |         last_ddl_time         
------------+---------------+------------+------------+------------+----------+-------------+-------
-------+-------------------------------+-------------------------------
 public     | warehouse_t12 | user1      |            | f          | f        | f           | user1 
       | 2022-12-01 20:28:15.708069+08 | 2022-12-01 20:28:15.708069+08
(1 row)
musicdb=>

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;

结果如下：

musicdb=> select datname,dattablespace,spcname from pg_database d,pg_tablespace t where d.dattablesace=t.oid;
  datname  | dattablespace |  spcname   
-----------+---------------+------------
 template1 |          1663 | pg_default
 omm       |          1663 | pg_default
 musicdb   |         16389 | music_tbs
 template0 |          1663 | pg_default
 postgres  |          1663 | pg_default
(5 rows)

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;

结果如下：

musicdb=> select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,rlowner  
from pg_class a  
where a.relkind in ('r', 'i')  
and reltablespace='0'  
order by a.relpages desc;
                    relname                     | relkind | relpages | pg_size_pretty | reltablespac
e | relowner 
------------------------------------------------+---------+----------+----------------+-------------
--+----------
 pg_attribute                                   | r       |      184 | 1472 kB        |             
0 |       10
 pg_proc                                        | r       |      140 | 1120 kB        |             
0 |       10
 pg_depend                                      | r       |       59 | 472 kB         |             
0 |       10
 pg_class                                       | r       |       52 | 416 kB         |             
0 |       10

 pg_proc_proname_args_nsp_new_index             | i       |       39 | 312 kB         |             
0 |       10
 pg_attribute_relid_attnam_index                | i       |       44 | 352 kB         |             
0 |       10
 pg_proc_proname_all_args_nsp_index             | i       |       41 | 328 kB         |           
省略n行。。。

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;j

结果如下：

musicdb=> \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,rlowner  
musicdb-> from pg_class a, pg_tablespace tb  
musicdb-> where a.relkind in ('r', 'i')  
musicdb-> and a.reltablespace=tb.oid  
musicdb-> and tb.spcname='ds_location1'  
musicdb-> order by a.relpages desc;
   relname   | relkind | relpages | pg_size_pretty | reltablespace | relowner 
-------------+---------+----------+----------------+---------------+----------
 warehose_t1 | r       |        0 | 0 bytes        |         16395 |    16391
(1 row)
musicdb=>


课后作业

1.创建表空间newtbs1、 ds_location1，查看表空间

musicdb=> create tablespace newtbs1 relative location 'tablespace/ds_location1';
CREATE TABLESPACE
musicdb=> \db
              List of tablespaces
     Name     | Owner |        Location         
--------------+-------+-------------------------
 ds_location1 | user1 | tablespace/tablespace_1
 music_tbs    | omm   | tablespace/test_ts1
 newtbs1      | user1 | tablespace/ds_location1
musicdb=>  pg_default   | omm   | 
 pg_global    | omm   | 
(5 rows)

2.创建一个数据库newdb1，默认表空间为newtbs1

musicdb=> create database newdb1 with tablespace=newtbs1;
CREATE DATABASE
musicdb=>

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 identified by 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
musicdb=> alter user user5 sysadmin;
ALTER 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=> create table newt1(col1 char(10)) tablespace ds_location1;
CREATE TABLE
newdb1=>

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 | tablecre
ator |            created            |         last_ddl_time         
------------+-----------+------------+--------------+------------+----------+-------------+---------
-----+-------------------------------+-------------------------------
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5   
     | 2022-12-01 20:56:54.249032+08 | 2022-12-01 20:56:54.249032+08
(1 row)
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,reowner  from pg_class a, pg_tablespace tb  
newdb1-> where a.relkind in ('r', 'i') and a.reltablespace=tb.oid and tb.spcname='newtbs1' order bya.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
(0 rows)

newdb1=> select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,reowner  from pg_class a, pg_tablespace tb  
newdb1-> where a.relkind in ('r', 'i') and a.reltablespace=tb.oid and tb.spcname='ds_location1' ordr by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 newt1   | r       |        0 | 0 bytes        |         16395 |    16404
(1 row)
newdb1=>
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