openGauss每日一练第10天 | 学习心得体会

学习目标

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。

本节要点

使用表空间，管理员可以控制一个数据库安装的磁盘布局。

表空间对应于一个文件系统目录，假定数据库节点数据目录/pg_location/mount1/path1是用户拥有读写权限的空目录。

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目录。

课后作业

测试环境：

root@modb:~# su - omm
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=#

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

创建用户test;
创建表空间t_tbspace;
将“t_tbspace”表空间的访问权限赋予数据用户test;
使用test用户在指定表空间t_tbspace创建表t1。

omm=# CREATE USER test IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# CREATE TABLESPACE t_tbspace RELATIVE LOCATION 'tablespace/t_tbspace1';
CREATE TABLESPACE
omm=# GRANT CREATE ON TABLESPACE t_tbspace TO test;
GRANT
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(i char(20)) 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 t where t.spcname like 't_tbspace';
  oid  |  spcname  | spcowner |         spcacl         | spcoptions | spcmaxsize | relative 
-------+-----------+----------+------------------------+------------+------------+----------
 16401 | t_tbspace |       10 | {omm=C/omm,test=C/omm} |            |            | t
(1 row)

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

omm=> with objectInDefaultTS as
          ( 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'
         )
 select * 
 from objectInDefaultTS 
   where relname not like 'pg_%' and relname not like 'gs_%' and relname not like 'sql_%'
 order by relpages desc;
 streaming_reaper_status_oid_index        | i       |        1 | 8192 bytes     |             0 |       10
 snapshot_pkey                            | i       |        1 | 8192 bytes     |             0 |       10
                 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
 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_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_relid_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_cont_query_matrelid_index      | i       |        1 | 8192 bytes     |             0 |       10
 streaming_stream                         | r       |        0 | 0 bytes        |             0 |       10
 snapshot                                 | r       |        0 | 0 bytes        |             0 |       10
 streaming_reaper_status                  | r       |        0 | 0 bytes        |             0 |       10
 streaming_cont_query                     | r       |        0 | 0 bytes        |             0 |       10
(21 rows)

omm=> 

4、查看数据库在非默认表空间下有哪些对象

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)),
          reltablespace,relowner
   from pg_class a, pg_tablespace tb
   where a.relkind in ('r', 'i')
   and a.reltablespace=tb.oid
   and tb.spcname='t_tbspace'
   order by a.relpages desc;

omm=>  relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 t1      | r       |        0 | 0 bytes        |         16401 |    16397
(1 row)

5、重命名表空间

注意：要在omm下，如在test下，执行会失败。
omm=> ALTER TABLESPACE t_tbspace RENAME TO app_tbs1;
ERROR:  permission denied for tablespace t_tbspace
DETAIL:  N/A	

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

6、删除表空间

注意：用户必须是表空间的owner或者系统管理员才能删除表空间。需要先删除表空间的对象，再删除表空间app_tbs：

omm=# drop table test.t1;
DROP TABLE
omm=# DROP TABLESPACE app_tbs;
DROP TABLESPACE
omm=#