PostgreSQL 参数优先级讲解

标签

PostgreSQL , 参数 , 优先级 , 配置文件 , alter system , 命令行 , 用户 , 数据库 , 所有用户 , 会话 , 事务 , 函数 , 表

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#%E8%83%8C%E6%99%AF 背景

PostgreSQL 参数配置包罗万象，可以在配置文件 , alter system , 命令行 , 用户 , 数据库 , 所有用户 , 会话 , 事务 , 函数 , 表 等层面进行配置，非常的灵活。

灵活是好，但是可配置的入口太多了，优先级如何？如果在多个入口配置了同一个参数的不同值，最后会以哪个为准？

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#%E5%8F%82%E6%95%B0%E4%BC%98%E5%85%88%E7%BA%A7 参数优先级

优先级如下，数值越大，优先级越高。

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#1-postgresqlconf 1 postgresql.conf

work_mem=1MB  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#2-postgresqlautoconf 2 postgresql.auto.conf

work_mem=2MB  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#3-command-line-options 3 command line options

work_mem=3MB  
  
pg_ctl start -o "-c work_mem='3MB'"  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#4-all-role 4 all role

work_mem=4MB  
  
alter role all set work_mem='4MB';  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#5-database 5 database

work_mem=5MB  
  
alter database postgres set work_mem='5MB';  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#6-role 6 role

work_mem=6MB  
  
alter role digoal set work_mem='6MB';  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#7-session-%E5%AE%A2%E6%88%B7%E7%AB%AF%E5%8F%82%E6%95%B0 7 session (客户端参数)

work_mem=7MB  
  
set work_mem ='7MB';  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#8-%E4%BA%8B%E5%8A%A1 8 事务

work_mem=8MB  
  
postgres=# begin;  
BEGIN  
postgres=# set local work_mem='8MB';  
SET  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#9-function 9 function

(参数在函数内有效，函数调用完成后依旧使用其他最高优先级参数值)

work_mem=9MB  
  
postgres=# create or replace function f_test() returns void as $$  
declare   
  res text;  
begin  
  show work_mem into res;  
  raise notice '%', res;                            
end;  
$$ language plpgsql strict set work_mem='9MB';  
CREATE FUNCTION  
  
postgres=# select f_test();  
NOTICE:  9MB  
 f_test   
--------  
   
(1 row)  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#10-table 10 table

TABLE相关参数（垃圾回收相关）

https://www.postgresql.org/docs/11/sql-createtable.html

autovacuum_enabled  
  
toast.autovacuum_enabled  
  
... ...   
  
autovacuum_vacuum_threshold  
  
toast.autovacuum_vacuum_threshold  
  
... ...  
           

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#%E5%B0%8F%E7%BB%93 小结

PostgreSQL 支持的配置入口：

配置文件(postgresql.conf) ,   
  
alter system(postgresql.auto.conf) ,   
  
命令行(postgres -o, pg_ctl -o) ,   
  
所有用户(alter role all set) ,   
  
数据库(alter database xxx set) ,   
  
用户(alter role 用户名 set)  ,   
  
会话(set xxx) ,   
  
事务(set local xxx;) ,   
  
函数(create or replace function .... set par=val;) ,   
  
表(表级垃圾回收相关参数)    
           

如果一个参数在所有入口都配置过，优先级如上，从上到下，优先级越来越大。

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#%E5%8F%82%E8%80%83 参考

《PostgreSQL GUC 参数级别介绍》 《连接PostgreSQL时,如何指定参数》

https://github.com/digoal/blog/blob/master/201901/20190130_03.md#%E5%85%8D%E8%B4%B9%E9%A2%86%E5%8F%96%E9%98%BF%E9%87%8C%E4%BA%91rds-postgresql%E5%AE%9E%E4%BE%8Becs%E8%99%9A%E6%8B%9F%E6%9C%BA 免费领取阿里云RDS PostgreSQL实例、ECS虚拟机