PostgreSQL服务器存储参数的内部查看方法和实际表述之间的关系

postgres=# show wal_buffers ;
 wal_buffers
-------------
 4MB
(1 row)

postgres=# show port;
 port
------
 5432
(1 row)

postgres=# select name,setting,unit,current_setting(name) from pg_settings where name = 'wal_buffers';
    name     | setting | unit | current_setting
-------------+---------+------+-----------------
 wal_buffers | 512     | 8kB  | 4MB
(1 row)

高速缓存

postgres=# select name,setting,unit,current_setting(name) from pg_settings where name='shared_buffers';
      name      | setting | unit | current_setting
----------------+---------+------+-----------------
 shared_buffers | 16384   | 8kB  | 128MB
(1 row)

物理布局

postgres=# show data_directory;
     data_directory     
-------------------------
 /var/lib/pgsql/9.4/data
(1 row)

postgres=# select name,setting from pg_settings where category='File Locations';
       name        |                 setting                
-------------------+-----------------------------------------
 config_file       | /var/lib/pgsql/9.4/data/postgresql.conf
 data_directory    | /var/lib/pgsql/9.4/data
 external_pid_file |
 hba_file          | /var/lib/pgsql/9.4/data/pg_hba.conf
 ident_file        | /var/lib/pgsql/9.4/data/pg_ident.conf
(5 rows)

数据库与OID的对应关系

postgres=# select datname,oid from pg_database where datname = 'postgres';
 datname  |  oid 
----------+-------
 postgres | 13003
(1 row)

表与OID，文件的对应关系

postgres=# select relname,oid,relfilenode from pg_class where relname = 'student'; relname |  oid  | relfilenode
---------+-------+-------------
 student | 24582 |       24582
(1 row)