openGauss每日一练第10天 | 学习心得体会（表空间的创建，用户授权，重命名【超好用】，删除）

摘要：
表空间是数据的容器。掌握表空间的管理，包括创建表空间、删除表空间、重命名表空间、查看表空间的情况。

表空间与文件系统关联，可以实现管理表空间的磁盘布局（通俗来说：就是管理文件的存放位置）

openGauss自带了两个表空间：pg_default和pg_global。
默认表空间pg_default：用来存储非共享系统表、用户表、用户表index、临时表、临时表index、内部临时表的默认表空间。对应存储目录为实例数据目录下的base目录。
共享表空间pg_global：用来存放共享系统表的表空间。对应存储目录为实例数据目录下的global目

随堂练习

1. 登录客户端并创建用户

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 user jack identified by 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE

2. 创建表空间、表

-- 创建表空间
omm=# CREATE TABLESPACE t_tbspace RELATIVE LOCATION 'tablespace/t_tbspace1';
CREATE TABLESPACE

--数据库系统管理员执行如下命令将“t_tbspace”表空间的访问权限赋予数据用户jack。
omm=# grant create on tablespace t_tbspace to jack;
GRANT
-- 连接到jack
omm=# \c omm jack
Password for user jack: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "omm" as user "jack".
omm=> 
-- 创建表
omm=> create table foo (i int) tablespace t_tbspace;
CREATE TABLE

-- 查看有哪些表空间:
-- 通过基础表查看
omm=# select oid,* from pg_tablespace;
  oid  |  spcname   | spcowner | spcacl | spcoptions | spcmaxsize | relative 
-------+------------+----------+--------+------------+------------+----------
  1663 | pg_default |       10 |        |            |            | f
  1664 | pg_global  |       10 |        |            |            | f
 16393 | t_tbspace  |       10 |        |            |            | t
(3 rows)
-- 通过元命令查看
omm=# \db
            List of tablespaces
    Name    | Owner |       Location        
------------+-------+-----------------------
 pg_default | omm   | 
 pg_global  | omm   | 
 t_tbspace  | omm   | tablespace/t_tbspace1
(3 rows)

3. 查看表空间t_tbspace的大小 ,调用函数 pg_tablespace_size

omm=> \q
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=# select pg_tablespace_size('t_tbspace');
 pg_tablespace_size 
--------------------
               8192
(1 row)

4. 查看数据库在默认表空间下有哪些对象(2种方式，查询及通过元命令查看)

omm=# with objectInDefaultTS as
omm-#           ( select relname, relkind, relpages,pg_size_pretty(pg_relation_size(a.oid)),
omm(#                   reltablespace,relowner
omm(#             from pg_class a
omm(#             where a.relkind in ('r', 'i')  and reltablespace='0'
omm(#          )
omm-#  select * 
omm-#  from objectInDefaultTS 
omm-#    where relname not like 'pg_%' and relname not like 'gs_%' and relname not like 'sql_%'
omm-#  order by relpages desc;
                 relname                  | relkind | relpages | pg_size_pretty | reltablespace | relowner 
------------------------------------------+---------+----------+----------------+---------------+----------
 streaming_gather_agg_index               | i       |        2 | 16 kB          |             0 |       10
 snapshot_id_key                          | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_lookupidxid_index   | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_schema_change_index | i       |        1 | 8192 bytes     |             0 |       10
 streaming_reaper_status_id_index         | i       |        1 | 8192 bytes     |             0 |       10
 streaming_reaper_status_oid_index        | i       |        1 | 8192 bytes     |             0 |       10
 snapshot_pkey                            | i       |        1 | 8192 bytes     |             0 |       10
 statement_history_time_idx               | i       |        1 | 8192 bytes     |             0 |       10
 streaming_stream_oid_index               | i       |        1 | 8192 bytes     |             0 |       10
 streaming_stream_relid_index             | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_relid_index         | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_defrelid_index      | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_id_index            | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_oid_index           | i       |        1 | 8192 bytes     |             0 |       10
 streaming_cont_query_matrelid_index      | i       |        1 | 8192 bytes     |             0 |       10
 plan_table_data                          | r       |        0 | 0 bytes        |             0 |       10
 statement_history                        | r       |        0 | 0 bytes        |             0 |       10
 streaming_reaper_status                  | r       |        0 | 0 bytes        |             0 |       10
 streaming_cont_query                     | r       |        0 | 0 bytes        |             0 |       10
--More-- streaming_stream                         | r       |        0 | 0 bytes        |             0 |       10
 snapshot                                 | r       |        0 | 0 bytes        |             0 |       10
(21 rows)

5. 查看数据库在非默认表空间下有哪些对象

omm=# --执行下面的SQL语句，查询数据库studentdb的非默认表空间t_tbspace下有哪些对象：
omm=#  select relname,relkind,relpages,pg_size_pretty(pg_relation_size(a.oid)),
omm-#           reltablespace,relowner
omm-#    from pg_class a, pg_tablespace tb
omm-#    where a.relkind in ('r', 'i')
omm-#    and a.reltablespace=tb.oid
omm-#    and tb.spcname='t_tbspace'
omm-#    order by a.relpages desc;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 foo     | r       |        0 | 0 bytes        |         16393 |    16389
(1 row)

6. 重命名表空间(语法 alter <old_tbs> rename to <new_tbs> ; )

omm=# alter tablespace t_tbspace rename to app_tbs;
ALTER TABLESPACE
omm=# \db
omm=#             List of tablespaces
    Name    | Owner |       Location        
------------+-------+-----------------------
 app_tbs    | omm   | tablespace/t_tbspace1
 pg_default | omm   | 
 pg_global  | omm   | 
(3 rows)

7. 删除表空间

PS：也顺手测试了一把，若是表空间有数据，是不允许删除的，从安全方面考虑，很安全，点赞+10086）

omm=# drop tablespace app_tbs;
ERROR:  tablespace "app_tbs" is not empty
omm=# drop table jack.foo;
DROP TABLE
omm=# drop tablespace app_tbs;
DROP TABLESPACE
omm=# 

课后练习

1、创建表空间t_tbspace、用户test，并使用test，在这个表空间上创建表t1

-- 创建表空间
omm=# create tablespace t_tbspace relative location 'tablespace/t_tbspace';
CREATE TABLESPACE

-- 创建用户
  
omm=# create user test identified by 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE

-- 授权读写表空间权限
omm=# grant create on tablespace t_tbspace to test;
GRANT

-- 连接用户test，并创建t1表
omm=# \c omm test
Password for user test: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "omm" as user "test".
omm=> create table t1(id int) tablespace t_tbspace;
CREATE TABLE
omm=> 

2、查看表空间t_tbspace的oid和大小

omm=> select oid,* from pg_tablespace;
  oid  |  spcname   | spcowner |         spcacl         | spcoptions | spcmaxsize | relative 
-------+------------+----------+------------------------+------------+------------+----------
  1663 | pg_default |       10 |                        |            |            | f
  1664 | pg_global  |       10 |                        |            |            | f
 16397 | t_tbspace  |       10 | {omm=C/omm,test=C/omm} |            |            | t
(3 rows)
-- 查看表空间大小
omm=> select pg_tablespace_size('t_tbspace');
 pg_tablespace_size 
--------------------
               8192
(1 row)

3、查看数据库在默认表空间下有哪些对象

查随堂练习4

4、查看数据库在非默认表空间下有哪些对象

查随堂练习4

5、重命名表空间(顺便验证了，无权限用户是不能重命名表空间的）

omm=> alter tablespace t_tbspace rename to app_tbs;
ERROR:  permission denied for tablespace t_tbspace
DETAIL:  N/A
omm=> 
omm=> \q
omm@modb:~$ gsql -r
omm=# alter tablespace t_tbspace rename to app_tbs;
ALTER TABLESPACE
omm=# \db
            List of tablespaces
    Name    | Owner |       Location       
------------+-------+----------------------
 app_tbs    | omm   | tablespace/t_tbspace
 pg_default | omm   | 
 pg_global  | omm   | 
(3 rows)

6、删除表空间

omm=# drop tablespace t_tbspace;
ERROR:  Tablespace "t_tbspace" does not exist.
omm=# drop tablespace app_tbs;
DROP TABLESPACE