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中，当我们在数据库中创建表的时候，明确指定在表空间中创建时，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.

学习内容

本章节学些了，数据库和表空间的关系。在openGauss数据库中，可以指定表创建到某个表空间下，如果不指定会默认到创建数据库指定的表空间。

1.创建表空间，创建数据库并指定一个默认的表空间1。如果不不指定会默认到pg_default

2.创建用户并权限sysadmin权限

3.再创建一个表空间2。

4.使用创建的用户登录到创建的数据库中，创建一张表指定到表空间2。并确实表空间2是否存在创建的表。

5.在指定的数据库中创建表，查询是否表默认到表空间1。

6.分别查询表空间1和表空间2的数据对象。

课后作业

1.创建表空间newtbs1、 ds_location1，查看表空间

openGauss=# CREATE TABLESPACE newtbs1 RELATIVE LOCATION 'tablespace/newtbs1';
CREATE TABLESPACE
openGauss=# CREATE TABLESPACE ds_location1 RELATIVE LOCATION 'tablespace/ds_location1';
CREATE DCREATE TABLESPACE
openGauss=# \db
                List of tablespaces
     Name     |   Owner   |        Location
--------------+-----------+-------------------------
 ds_location1 | opengauss | tablespace/ds_location1
 newtbs1      | opengauss | tablespace/newtbs1
 pg_default   | opengauss |
 pg_global    | opengauss |
(4 rows)

2.创建一个数据库newdb1，默认表空间为 newtbs1。

openGauss=# CREATE DATABASE newdb1  WITH TABLESPACE = newtbs1;
CREATE DATABASE
openGauss=# \l+
                                                                List of databases
   Name    |   Owner   | Encoding  | Collate | Ctype |    Access privileges    |  Size  | Tablespace |                Description
-----------+-----------+-----------+---------+-------+-------------------------+--------+------------+--------------------------------------------
 musicdb1  | opengauss | SQL_ASCII | C       | C     |                         | 13 MB  | pg_default |
 musicdb2  | opengauss | SQL_ASCII | C       | C     |                         | 13 MB  | pg_default |
 newdb1    | opengauss | SQL_ASCII | C       | C     |                         | 13 MB  | newtbs1    |
 postgres  | opengauss | SQL_ASCII | C       | C     |                         | 387 MB | pg_default | default administrative connection database
 template0 | opengauss | SQL_ASCII | C       | C     | =c/opengauss           +| 12 MB  | pg_default | default template for new databases
           |           |           |         |       | opengauss=CTc/opengauss |        |            |
 template1 | opengauss | SQL_ASCII | C       | C     | =c/opengauss           +| 12 MB  | pg_default | unmodifiable empty database
           |           |           |         |       | opengauss=CTc/opengauss |        |            |
(6 rows)

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）

openGauss=# CREATE USER user5 IDENTIFIED BY 'test@1234';
CREATE ROLE
openGauss=# ALTER USER user5 SYSADMIN;
ALTER ROLE
openGauss=# \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 jack      |                                                                                                                  | {}
 opengauss | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}
 user5     | Sysadmin               

访问数据库并建表

openGauss=# \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(product_id integer,product_name char(20),category char(30)) tablespace ds_location1;
CREATE TABLE
newdb1=> create table newt12(product_id integer,product_name char(20),category char(30));
CREATE TABLE
newdb1=> \dt+
                                     List of relations
 Schema |  Name  | Type  | Owner |  Size   |             Storage              | Description
--------+--------+-------+-------+---------+----------------------------------+-------------
 public | newt1  | table | user5 | 0 bytes | {orientation=row,compression=no} |
 public | newt12 | table | user5 | 0 bytes | {orientation=row,compression=no} |
(2 rows)

4.查看表所在的表空间

newdb1=> select * from pg_tables where tablename like 'newt%';
 schemaname | tablename | tableowner |  tablespace  | hasindexes | hasrules | hastriggers | tablecreator |            created            |         last_ddl_time
------------+-----------+------------+--------------+------------+----------+-------------+--------------+-------------------------------+-------------------------------
 public     | newt1     | user5      | ds_location1 | f          | f        | f           | user5        | 2022-12-01 11:07:46.098793+08 | 2022-12-01 11:07:46.098793+08
 public     | newt12    | user5      |              | f          | f        | f           | user5        | 2022-12-01 11:09:11.516481+08 | 2022-12-01 11:09:11.516481+08
(2 rows)
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          | newt12     | BASE TABLE
 newdb1        | public          | newt1      | BASE TABLE
(5 rows)

5.查看表空间newtbs1、 ds_location1上的对象3

openGauss=# \c newdb1 user1
Password for user user1:
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "newdb1" as user "user1".
newdb1=>
newdb1=>
newdb1=>
newdb1=> select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),reltablespace,relowner
newdb1-> from pg_class a
newdb1-> where a.relkind in ('r', 'i')
newdb1-> and reltablespace='0'
newdb1-> and relname not like 'gs%'
newdb1-> and relname not like 'pg%'
newdb1-> and relname not like 's%'
newdb1-> order by a.relpages desc;
     relname     | relkind | relpages | pg_size_pretty | reltablespace | relowner
-----------------+---------+----------+----------------+---------------+----------
 newt12          | r       |        0 | 0 bytes        |             0 |    18922
 plan_table_data | r       |        0 | 0 bytes        |             0 |       10
(2 rows)
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-> order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner
---------+---------+----------+----------------+---------------+----------
 newt1   | r       |        0 | 0 bytes        |         18920 |    18922
(1 row)