openGauss每日一练第 7 天 |学习笔记

原创 newdata 2022-11-30

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openGauss每日一练第7天

今日目标：学习openGauss数据库、用户和模式的关系和访问方式，理解模式是在数据库层面，用户是在实例层面

了解schema的基本概念及常用命令

SCHEMA

SCHEMA又称作模式。通过管理SCHEMA，允许多个用户使用同一数据库而不相互干扰，可以将数据库对象组织成易于管理的逻辑组，同时便于将第三方应用添加到相应的SCHEMA下而不引起冲突。

每个数据库包含一个或多个SCHEMA。数据库中的每个SCHEMA包含表和其他类型的对象。数据库创建初始，默认具有一个名为PUBLIC的SCHEMA，且所有用户都拥有此SCHEMA的USAGE权限，只有系统管理员和初始化用户可以在PUBLIC SCHEMA下创建函数、存储过程和同义词对象，其他用户即使赋予CREATE权限后也不可以创建上述三种对象。可以通过SCHEMA分组数据库对象。SCHEMA类似于操作系统目录，但SCHEMA不能嵌套。

相同的数据库对象名称可以应用在同一数据库的不同SCHEMA中，而没有冲突。例如，a_schema和b_schema都可以包含名为mytable的表。具有所需权限的用户可以访问数据库的多个SCHEMA中的对象。

通过CREATE USER创建用户的同时，系统会在执行该命令的数据库中，为该用户创建一个同名的SCHEMA。

创建和管理schema

1.实验准备

创建表空间music_tbs ，并在该表空间下创建数据库musicdb

创建user1，并授予sysadmin权限

omm=# create tablespace music_tbs relative location 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# create database musicdb with tablespace = music_tbs ;
CREATE DATABASE
omm=# create user user1 sysadmin identified by 'gauss@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# \l 
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 musicdb   | omm   | UTF8     | C       | C     | 
 omm       | omm   | UTF8     | C       | C     | 
 postgres  | omm   | UTF8     | C       | C     | 
 template0 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
 template1 | omm   | UTF8     | C       | C     | =c/omm           +
           |       |          |         |       | omm=CTc/omm
(5 rows)

omm=# \dt
No relations found.
omm=# \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Me
mber of 
-----------+------------------------------------------------------------------------------------------------------------------+---
--------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

omm=#

2.课后作业

2.1 查看当前数据库下有哪些模式(schema)

\q // quit gsql

\dn[S+] [PATTERN] // list schemas

omm=# \q
omm@modb:~$ gsql -d musicdb -p 5432 -U user1 -W gauss@1234 -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.

musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
(10 rows)

musicdb=> \dn+
                                         List of schemas
      Name       | Owner | Access privileges |           Description            | WithBlockChain 
-----------------+-------+-------------------+----------------------------------+----------------
 blockchain      | omm   |                   | blockchain schema                | f
 cstore          | omm   |                   | reserved schema for DELTA tables | f
 db4ai           | omm   | omm=UC/omm       +| db4ai schema                     | f
                 |       | =U/omm            |                                  | 
 dbe_perf        | omm   |                   | dbe_perf schema                  | f
 dbe_pldebugger  | omm   | omm=UC/omm       +| dbe_pldebugger schema            | f
                 |       | =U/omm            |                                  | 
 dbe_pldeveloper | omm   | omm=UC/omm       +| dbe_pldeveloper schema           | f
                 |       | =U/omm            |                                  | 
 pkg_service     | omm   |                   | pkg_service schema               | f
 public          | omm   | omm=UC/omm       +| standard public schema           | f
 sqladvisor      | omm   | omm=UC/omm       +| sqladvisor schema                | f
                 |       | =U/omm            |                                  | 
(10 rows)

                 |       | =U/omm            |                                  | 
 snapshot        | omm   |                   | snapshot schema                  | f
musicdb=>

2.2 然后为数据库musicdb创建4个模式，名称自定义

创建schema语法

根据指定的名称创建模式。

CREATE SCHEMA schema_name
[ AUTHORIZATION user_name ] [WITH BLOCKCHAIN] [ schema_element [ … ] ];

根据用户名创建模式

CREATE SCHEMA AUTHORIZATION user_name [ schema_element [ … ] ];

schema查看

使用gsql查看

\dn+

– 执行SQL语句，查看某个数据库下有哪些模式
select catalog_name,schema_name,schema_owner from information_schema.schemata ;

Information Schema

信息模式本身是一个名为information_schema的模式。这个模式自动存在于所有数据库中。信息模式由一组视图构成，它们包含定义在当前数据库中对象的信息。这个模式的拥有者是初始数据库用户，并且该用户自然地拥有这个模式上的所有特权，包括删除它的能力。

information_schema.schemata

设置所属的模式。

SET [ SESSION | LOCAL ]
{CURRENT_SCHEMA { TO | = } { schema | DEFAULT }
| SCHEMA ‘schema’};

musicdb=> create schema schm1 authorization user1;
CREATE SCHEMA
musicdb=> create schema schm2 authorization user2;
ERROR:  role "user2" does not exist
musicdb=> create schema schm2 authorization user;;
musicdb=> ^C
musicdb=> create schema schm2 authorization user1;
musicdb=> CREATE SCHEMA
musicdb=> 
      
musicdb=> create schema schm3 authorization user1;
CREATE SCHEMA
musicdb=> create schema schm4 authorization user1;
CREATE SCHEMA
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 schm1           | user1
 schm2           | user1
 schm3           | user1
 schm4           | user1
 snapshot        | omm
 sqladvisor      | omm
 musicdb=> select catalog_name,schema_name,schema_owner from information_schema.schemata ;
 catalog_name |    schema_name     | schema_owner 
--------------+--------------------+--------------
 musicdb      | pg_toast           | omm
 musicdb      | cstore             | omm
 musicdb      | pkg_service        | omm
 musicdb      | dbe_perf           | omm
 musicdb      | snapshot           | omm
 musicdb      | blockchain         | omm
 musicdb      | pg_catalog         | omm
 musicdb      | public             | omm
 musicdb      | sqladvisor         | omm
 musicdb      | dbe_pldebugger     | omm
 musicdb      | dbe_pldeveloper    | omm
 musicdb      | information_schema | omm
 musicdb      | db4ai              | omm
 musicdb      | schm1              | user1
 musicdb      | schm2              | user1
 musicdb      | schm3              | user1
 musicdb      | schm4              | user1

2.3 在数据库musicdb的不同的模式下创建同名的表

musicdb=> create table schm1.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm2.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm3.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm4.ttt(col varchar(100));
CREATE TABLE
musicdb=> 
musicdb=> insert into schm1.ttt values('hello schema schm1   11111');
INSERT 0 1
musicdb=> insert into schm2.ttt values('hello schema schm2   22222');
INSERT 0 1
musicdb=> insert into schm3.ttt values('hello schema schm3   33333');
INSERT 0 1
musicdb=> insert into schm4.ttt values('hello schema schm4   44444');
INSERT 0 1
musicdb=> \dt
No relations found.
musicdb=> \dt
No relations found.
musicdb=> \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of 
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 schm1           | user1
 schm2           | user1
 schm3           | user1
 schm4           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

musicdb=> set current_schema to schm1;
SET
musicdb=> \dt
                        List of relations
 Schema | Name | Type  | Owner |             Storage              
--------+------+-------+-------+----------------------------------
 schm1  | ttt  | table | user1 | {orientation=row,compression=no}
(1 row)

musicdb=> 
musicdb=> create or replace view my_tables as
musicdb->  select table_catalog, table_schema, table_name, table_type
musicdb-> from information_schema.tables
musicdb-> where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');
CREATE VIEW
musicdb=> select * from my_tables ;
 table_catalog |  table_schema   | table_name | table_type 
---------------+-----------------+------------+------------
 musicdb       | db4ai           | snapshot   | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_errors  | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_source  | BASE TABLE
 musicdb       | public          | my_tables  | VIEW
 musicdb       | schm4           | ttt        | BASE TABLE
 musicdb       | schm3           | ttt        | BASE TABLE
 musicdb       | schm2           | ttt        | BASE TABLE
 musicdb       | schm1           | ttt        | BASE TABLE
(8 rows)

musicdb=>

2.4.访问musicdb数据库下不同模式的同名表

 musicdb=> show search_path;
  search_path   
----------------
 "$user",public
(1 row)

musicdb=> select * from schm1.ttt ;
            col             
----------------------------
 hello schema schm1   11111
(1 row)

musicdb=> select * from schm2.ttt ;
musicdb=>             col             
----------------------------
 hello schema schm2   22222
(1 row)


musicdb=> select * from schm3.ttt ;
(1 row)

musicdb=>             col             
----------------------------
 hello schema schm3   33333

musicdb=> select * from schm4.ttt ;
            col             
----------------------------
 hello schema schm4   44444
(1 row)

musicdb=>

实验理解：模式是在数据库层面，用户是在实例层面

--登录musicdb数据库，查看用户和模式
musicdb=> \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of 
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

musicdb=> \dt
No relations found.
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 schm1           | user1
 schm2           | user1
 schm3           | user1
 schm4           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

musicdb=> \q

-- 登录omm数据库，查看用户和模式
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=# \du
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of 
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

omm=# \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 user1           | user1
(11 rows)

omm=#

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