3.PG查看系统信息的常用命令

1.查看当前数据库实例的版本信息

postgres=# select version();
                                                 version                                                 
---------------------------------------------------------------------------------------------------------
 PostgreSQL 14.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
(1 row)

2.查看数据库的启动时间

postgres=# select pg_postmaster_start_time();
   pg_postmaster_start_time    
-------------------------------
 2023-12-16 09:52:59.531553+08
(1 row)

3.查看最后load配置时间

postgres=# select pg_conf_load_time();
       pg_conf_load_time       
-------------------------------
 2023-12-16 09:54:44.140466+08
(1 row)

4.查看当前数据库时区

postgres=# show timezone;
   TimeZone    
---------------
 Asia/Shanghai
(1 row)

5.查看当前时间

postgres=# select now();
             now             
-----------------------------
 2023-12-18 21:55:17.3275+08
(

6.查看当前数据库服务器的ip地址和端口

postgres=# select inet_server_addr(),inet_server_port();
 inet_server_addr | inet_server_port 
------------------+------------------
                  |                 
(1 row)

7.查询当前session的后台服务器进程的PID

postgres=# select pg_backend_pid();
 pg_backend_pid 
----------------
           3449
(1 row

8.查看当前参数配置情况

postgres=# show shared_buffers;
 shared_buffers 
----------------
 128MB

9.修改当前session的参数配置

postgres=# set maintenance_work_mem to '128MB';
SET

11.查看数据库大小

postgres=# select pg_database_size('postgres'),pg_size_pretty(pg_database_size('postgres'));
 pg_database_size | pg_size_pretty 
------------------+----------------
          8758051 | 8553 kB