openGauss每日一练第10天 | 学习心得体会

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
CREATE USER test IDENTIFIED BY 'Kunpeng@1234';
CREATE TABLESPACE t_tbspace RELATIVE LOCATION 'tablespace/t_tbspace1';
--将t_tbspace表空间的访问权限赋予数据用户test
GRANT CREATE ON TABLESPACE t_tbspace TO test;
--创建表t1
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 int) TABLESPACE t_tbspace;
CREATE TABLE

2、查看表空间t_tbspace的oid和大小

omm=> SELECT PG_TABLESPACE_SIZE('t_tbspace');
 pg_tablespace_size 
--------------------
               8192
(1 row)

omm=> select oid from pg_tablespace where spcname='t_tbspace';
  oid  
-------
 16400
(1 row)

3、查看数据库在默认表空间下有哪些对象

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;
                 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
 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
 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_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_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)

4、查看数据库在非默认表空间下有哪些对象

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;
 relname | relkind | relpages | pg_size_pretty | reltablespace | relowner 
---------+---------+----------+----------------+---------------+----------
 t1      | r       |        0 | 0 bytes        |         16400 |    16401
(1 row)

5、重命名表空间

omm=# \db
            List of tablespaces
    Name    | Owner |       Location        
------------+-------+-----------------------
 app_ts     | omm   | tablespace/app_ts1
 enmtbs     | omm   | tablespace/enmtbs1
 pg_default | omm   | 
 pg_global  | omm   | 
 t_tbspace  | omm   | tablespace/t_tbspace1
(5 rows)

omm=# ALTER TABLESPACE t_tbspace RENAME TO app_tbs;
ALTER TABLESPACE
omm=# \db
            List of tablespaces
    Name    | Owner |       Location        
------------+-------+-----------------------
 app_tbs    | omm   | tablespace/t_tbspace1
 app_ts     | omm   | tablespace/app_ts1
 enmtbs     | omm   | tablespace/enmtbs1
 pg_default | omm   | 
 pg_global  | omm   | 
(5 rows)

6、删除表空间

--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_ts：
omm=# DROP TABLESPACE app_tbs;
ERROR:  tablespace "app_tbs" is not empty
omm=# drop table test.t1 ;
DROP TABLE
omm=# DROP TABLESPACE app_tbs;
DROP TABLESPACE
omm=# \db
           List of tablespaces
    Name    | Owner |      Location      
------------+-------+--------------------
 app_ts     | omm   | tablespace/app_ts1
 enmtbs     | omm   | tablespace/enmtbs1
 pg_default | omm   | 
 pg_global  | omm   | 
(4 rows)