整理了postgresql的系统表关联的常用SQL，如下：
–查看数据库  www.2cto.com  
select * from pg_database;
 
–查看表空间
select * from pg_tablespace;
 
–查看语言
select * from pg_language;
 
–查看角色用户
select * from pg_user;
select * from pg_shadow;
select * from pg_roles;
 
–查看会话进程
select * from pg_stat_activity;
 
–查看表
SELECT * FROM pg_tables where schemaname = ‘public’;
 
–查看表字段
select * from information_schema.columns where table_schema = ‘public’ and table_name = ‘pf_vip_org’;
 
–查看视图
select * from pg_views where schemaname = ‘public’;
select * from information_schema.views where table_schema = ‘public’;
 
–查看触发器
select * from information_schema.triggers;
 
–查看序列
select * from information_schema.sequences where sequence_schema = ‘public’;
 
 –查看约束
select * 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
select * 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 from pg_class a,pg_index b where a.oid = b.indrelid and a.relname = ‘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
select b.indexrelid from pg_class a,pg_index b where a.oid = b.indrelid and a.relname = ‘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
select * 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)
select * from pg_stat_database
 
–查看索引的使用情况
select * 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*8 as index_size_kb     
  FROM pg_namespace n,
       pg_class bc,             — base class
       pg_class ic,             — index class
       pg_index i,
       pg_attribute a,           — 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 = ‘public’
     and bc.relname = ‘cc’
  ORDER BY schema_name, table_name, index_name, attname;
 
–查看PG锁
select * 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, c.relname 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    AS (SELECT oid, fqname FROM fq_objects WHERE relkind = ‘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’;