openGauss每日一练第8天 一个数据库可以存储在多个表空间中

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

测试同一个数据库,创建表存储在非默认表空间中。

课后作业

1.创建表空间newtbs1、 ds_location1，查看表空间

--创建表空间newtbs1、 ds_location1
/*
DROP tablespace IF EXISTS newtbs1;
CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/test_newtbs1';
DROP tablespace IF EXISTS ds_location1;
CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/test_ds_location1';
*/
omm=# DROP tablespace IF EXISTS newtbs1;
NOTICE:  Tablespace "newtbs1" does not exist, skipping.
DROP TABLESPACE
omm=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/test_newtbs1';
CREATE TABLESPACE
omm=# DROP tablespace IF EXISTS ds_location1;
NOTICE:  Tablespace "ds_location1" does not exist, skipping.
DROP TABLESPACE
omm=# CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/test_ds_location1';
CREATE TABLESPACE

--查看表空间
omm=# \db
                 List of tablespaces
     Name      | Owner |           Location           
---------------+-------+------------------------------
 ds_location1  | omm   | tablespace/test_ds_location1
 music_tbs     | omm   | tablespace/test_ts1
 music_tbs1    | omm   | tablespace/test_ts12
 musicdb10_tbs | omm   | tablespace/test_ts10
 newtbs1       | omm   | tablespace/test_newtbs1
 pg_default    | omm   | 
 pg_global     | omm   | 
(7 rows)

2.创建一个数据库newdb1，默认表空间为newtbs1

--创建数据库
/*
DROP DATABASE  IF EXISTS  newdb1;
CREATE DATABASE newdb1 WITH TABLESPACE = newtbs1;
*/
omm=# DROP DATABASE  IF EXISTS  newdb1;
NOTICE:  database "newdb1" does not exist, skipping
DROP DATABASE
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）

--创建用户user5，并授予SYSADMIN权限
/*
CREATE USER user5 IDENTIFIED BY 'meiriyilian@1234';
ALTER USER user1 SYSADMIN;
*/
omm=# CREATE USER user5 IDENTIFIED BY 'meiriyilian@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user5 SYSADMIN;
ALTER ROLE


--访问数据库newdb1，在表空间ds_location1上，创建一个表newt1
/*
\c newdb1 user5
create table newt1(id integer, comm char(20)) tablespace ds_location1;
*/
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(id integer, comm char(20)) tablespace ds_location1;
CREATE TABLE

4.查看表所在的表空间

--查看newdb1数据库目前有哪些表：
newdb1=> select table_catalog, table_schema, table_name, table_type
newdb1-> from information_schema.tables
newdb1-> where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');
 table_catalog |  table_schema   | table_name | table_type 
---------------+-----------------+------------+------------
 newdb1        | db4ai           | snapshot   | BASE TABLE
 newdb1        | dbe_pldeveloper | gs_errors  | BASE TABLE
 newdb1        | dbe_pldeveloper | gs_source  | BASE TABLE
 newdb1        | public          | newt1      | BASE TABLE
(4 rows)

--查询pg_tables：     select * from pg_tables where tablename = 'newt1';
newdb1=> select * from pg_tables where tablename = 'newt1';
 schemaname | tablename | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablecreator |            cr
eated            |         last_ddl_time         
------------+-----------+------------+--------------+------------+----------+-------------+--------------+--------------
-----------------+-------------------------------
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5        | 2022-12-12 22
:04:13.084053+08 | 2022-12-12 22:04:13.084053+08
(1 row)

--确认表newt1所在的表空间为指定的ds_location1。

5.查看表空间newtbs1、 ds_location1上的对象

/*
\c newdb1 user5
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;
*/

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-> newdb1-> and a.reltablespace=tb.oid  
newdb1-> and tb.spcname='ds_location1'
order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 newt1   | r       |        0 | 0 bytes        |         16482 |    16483
(1 row)


/*
create table newt2(id integer, comm char(20));

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;
*/

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'
newdb1-> order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
(0 rows)