转自：http://my.oschina.net/Kenyon/blog/85395?fromerr=tNxqr6NN

整理了postgresql的系统表关联的常用sql，如下：

--查看数据库
select * from pg_database;

--查看表空间
from pg_tablespace;

--查看语言
from pg_language;

--查看角色用户
from pg_user;
from pg_shadow;
from pg_roles;

--查看会话进程
from pg_stat_activity;

--查看表
SELECT * FROM pg_tables where schemaname = 'public';

--查看表字段
from information_schema.columns where table_schema = 'public' and table_name = 'pf_vip_org';

--查看视图
from pg_views 'public';
from information_schema.views --查看触发器
triggers;

--查看序列
from information_schema.sequences where sequence_schema = 'public';

 --查看约束
from pg_constraint where contype = 'p' --u unique,p primary,f foreign,c check,t trigger,x exclusion select a.relname as table_name,b.conname as constraint_name,b.contype as constraint_type from pg_class a,pg_constraint b where a.oid = b.conrelid and a.relname = 'cc';

--查看索引
from pg_index ;

--查看表上存在哪些索引以及大小
select relname,n.amname as index_type from pg_class m,pg_am n where m.relam = n.oid and m.oid in ( select b.indexrelid where a.oid = b.indrelid 'cc');

SELECT c.relname,c2.relname,c2.relpages*8 as size_kb FROM pg_class c,pg_class c2,pg_index i WHERE c.relname = 'cc' AND c.oid = i.indrelid AND c2.oid = i.indexrelid ORDER BY c2.relname; 

--查看索引定义
'cc';
select pg_get_indexdef(b.indexrelid);

--查看过程函数定义
select oid,* from pg_proc where proname = 'insert_platform_action_exist'; --oid = 24610
from pg_get_functiondef(24610);

--查看表大小(不含索引等信息)
select pg_relation_size('cc');                         --368640 byte
select pg_size_pretty(pg_relation_size('cc')) --360 kB --查看DB大小 select pg_size_pretty(pg_database_size('smiletao'));   --12M

--查看服务器DB运行状态
[postgres@eyar ~]$ pg_ctl status -D $PGDATA
pg_ctl: server is running (PID: 2373)
/home/postgres/bin/postgres "-D" "/database/pgdata" 

--查看每个DB的使用情况(读,写,缓存,更新,事务等)
from pg_stat_database --查看索引的使用情况 from pg_stat_user_indexes;

--查看表所对应的数据文件路径与大小
SELECT pg_relation_filepath(oid),relpages FROM pg_class WHERE relname = 'empsalary';

--查看索引与相关字段及大小
 SELECT n.nspname AS schema_name,r.rolname as table_owner,bc.relname AS table_name,ic.relname AS index_name,a.attname AS column_name,bc.relpages*as index_size_kb FROM pg_namespace n,pg_class bc,-- base class pg_class ic,161)">-- index class pg_index i,pg_attribute a,161)">-- att in base pg_roles r WHERE bc.relnamespace = n.oid and i.indrelid = bc.oid and i.indexrelid = ic.oid and bc.relowner = r.oid and i.indkey[0] = a.attnum and i.indnatts = 1 and a.attrelid = bc.oid and n.nspname = and bc.relname = BY schema_name,table_name,index_name,attname;

--查看PG锁
from pg_locks;

备注：relpages*8 是实际所占磁盘大小

--查看表空间大小
select pg_tablespace_size('pg_default');

--查看序列与表的对应关系
  WITH fq_objects AS (SELECT c.oid,c.relname AS fqname,c.relkind,0)">AS relation FROM pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace ),sequences AS (SELECT oid,fqname FROM fq_objects WHERE relkind = 'S'),tables 'r' ) SELECT s.fqname AS sequence,'->' as depends,t.fqname AS table FROM pg_depend d JOIN sequences s ON s.oid = d.objid JOIN tables t ON t.oid = d.refobjid WHERE d.deptype = 'a' and t.fqname = 'cc';