查看系统表
除了创建的表以外,数据库还包含很多系统表。这些系统表包含集群安装信息以及GaussDB(DWS)上运行的各种查询和进程的信息。可以通过查询系统表来收集有关数据库的信息。
系统表和系统视图中每个表的说明指出了表是对所有用户可见还是只对初始化用户可见。必须以初始化用户身份登录才能查询只对初始化用户可见的表。
查看数据库中包含的表
例如,在PG_TABLES系统表中查看public schema中包含的所有表。
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SELECT distinct(tablename) FROM pg_tables WHERE SCHEMANAME = 'public';
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结果类似如下这样:
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tablename
-------------------
err_hr_staffs
test
err_hr_staffs_ft3
web_returns_p1
mig_seq_table
films4
(6 rows)
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查看数据库用户
通过PG_USER可以查看数据库中所有用户的列表,还可以查看用户ID(USESYSID)和用户权限。
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SELECT * FROM pg_user;
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usename | usesysid | usecreatedb | usesuper | usecatupd | userepl | passwd | valbegin | valuntil | respool
| parent | spacelimit | useconfig
-----------------------------------+----------+-------------+----------+-----------+---------+----------+----------+----------+----------
----+--------+------------+-----------
dfc22b86afbd9a745668c3ecd0f15ec18 | 17107 | f | f | f | f | ******** | | | default_p
ool | 0 | |
guest | 17103 | f | f | f | f | ******** | | | default_p
ool | 0 | |
Ruby | 10 | t | t | t | t | ******** | | | default_p
ool | 0 | |
dbadmin | 16404 | f | f | f | f | ******** | | | default_p
ool | 0 | |
lily | 16482 | f | f | f | f | ******** | | | default_p
ool | 0 | |
jack | 16478 | f | f | f | f | ******** | | | default_p
ool | 0 | |
(6 rows)
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GaussDB(DWS)在内部使用Ruby执行日常管理和维护任务。可以向SELECT语句添加WHERE usesysid > 10来筛选查询,使其只显示用户定义的用户名称。
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SELECT * FROM pg_user WHERE usesysid > 10;
usename | usesysid | usecreatedb | usesuper | usecatupd | userepl | passwd | valbegin | valuntil | respool
| parent | spacelimit | useconfig
-----------------------------------+----------+-------------+----------+-----------+---------+----------+----------+----------+----------
----+--------+------------+-----------
dfc22b86afbd9a745668c3ecd0f15ec18 | 17107 | f | f | f | f | ******** | | | default_p
ool | 0 | |
guest | 17103 | f | f | f | f | ******** | | | default_p
ool | 0 | |
dbadmin | 16404 | f | f | f | f | ******** | | | default_p
ool | 0 | |
lily | 16482 | f | f | f | f | ******** | | | default_p
ool | 0 | |
jack | 16478 | f | f | f | f | ******** | | | default_p
ool | 0 | |
(5 rows)
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查看数据库用户属性
通过PG_AUTHID可以查看数据库中所有用户的属性列表。
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SELECT * FROM pg_authid;
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rolname | rolsuper | rolinherit | rolcreaterole | rolcreatedb | rolcatupdate | rolcanlogin | rolreplication | rolauditadmin | rolsystemadmin | rolconnlimit | rolpassword | rolvalidbegin | rolvaliduntil | rolrespool | roluseft | rolparentid | roltabspace | rolkind | rolnodegroup | roltempspace | rolspillspace | rolexcpdata | rolmonitoradmin | roloperatoradmin | rolpolicyadmin
---------+----------+------------+---------------+-------------+--------------+-------------+----------------+---------------+----------------+--------------+------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------
--------+---------------+--------------+----------+-------------+-------------+---------+--------------+--------------+---------------+-------------+-----------------+------------------+----------------
dbadmin | f | t | f | f | f | t | f | f | t | -1 | sha256ce0ea617e7b7c0f2d38b00a12261b5e98ce18c218
89a30ebf410631c52f882d376141f31b47b67b0ceec9d10c931358140d276009bd8d19ac6a5647558c8b70d009986e774c2ba9563e42f4331629379d40720e4a3e0997c2b592833db778908md5eb0c1ffc5c76ef6272debb03f585b0b9ecdfecefade |
| | default_pool | f | 0 | | n | | | | | f | f | f
Ruby | t | t | t | t | t | t | t | t | t | -1 | sha256d2058470eb2cead16d1d85a2b69207bc33e020bd4
530b67102c9c237dd2cb5d1ebae9d98c88ebf8f51950a333a4bb436488df40e645eb3d346af6c401c8fe5f83b2087349dcccf38fd1eb8ec828b27f28af4e5066549ba0bb6d249f82c664151md5417898ceaa6a205cb03d1b8df8fb92f7ecdfecefade |
| | default_pool | t | 0 | | n | 0 | | | | t | t | t
(2 rows)
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查看新建用户joe的权限:
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SELECT * FROM pg_authid where rolname = 'joe';
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查看和停止正在运行的查询语句
通过视图PG_STAT_ACTIVITY 可以查看正在运行的查询语句。方法如下:
- 设置参数track_activities为on。
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SET track_activities = on;
当此参数为on时,数据库系统才会收集当前活动查询的运行信息。
- 查看正在运行的查询语句。以查看正在运行的查询语句所连接的数据库名、执行查询的用户、查询状态及查询对应的PID为例:
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SELECT datname, usename, state,pid FROM pg_stat_activity;
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datname | usename | state | pid ----------+---------+--------+----------------- postgres | Ruby | active | 140298793514752 postgres | Ruby | active | 140298718004992 postgres | Ruby | idle | 140298650908416 postgres | Ruby | idle | 140298625742592 postgres | dbadmin | active | 140298575406848 (5 rows)
如果state字段显示为idle,则表明此连接处于空闲,等待用户输入命令。
如果仅需要查看非空闲的查询语句,则使用如下命令查看:
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SELECT datname, usename, state FROM pg_stat_activity WHERE state != 'idle';
- 若需要取消运行时间过长的查询,通过PG_TERMINATE_BACKEND函数,根据线程ID结束会话。
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SELECT PG_TERMINATE_BACKEND(pid);
显示类似如下信息,表示结束会话成功。
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PG_TERMINATE_BACKEND ---------------------- t (1 row)
显示类似如下信息,表示用户执行了结束当前会话的操作。1 2
FATAL: terminating connection due to administrator command FATAL: terminating connection due to administrator command
gsql客户端使用PG_TERMINATE_BACKEND函数结束当前会话后台线程时,客户端不会退出而是自动重连。即还会返回“The connection to the server was lost. Attempting reset: Succeeded.”
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FATAL: terminating connection due to administrator command FATAL: terminating connection due to administrator command The connection to the server was lost. Attempting reset: Succeeded.