1，提工单
由于当初设计都是用的public schema，而public schema对所有用户权限没有限制，所以需要回收部分用户的建表权限，
=> dn
List of schemas
Name | Owner
--------+-----------
public | pg2490375
而public 默认owner是初始化实列的用户，所以提供单将public owner改成自己建的用户
将test,template1数据库public schema的owner给xhc_test 。
=> dn
List of schemas
Name | Owner
--------+----------
public | xhc_test
2，若为rds_superuser 则改为nords_superuser
xhc_dba=> alter user xhc_rw nords_superuser;
3，回收create 权限
xhc_dba=> revoke create on schema public from public;
xhc_dba=> c - xhc_rw;
You are now connected to database "xhc_dba" as user "xhc_rw”. —回收成功
xhc_dba=> create table t000(id serial,id2 bigint);
ERROR: permission denied for schema public
xhc_dba=>
注1
单单回收某个用户的create权限是没有用的，必须回收public的create权限，
hc_dba=> revoke create on schema public from xhc_rw;
REVOKe
xhc_dba=> c - xhc_rw;
You are now connected to database "xhc_dba" as user "xhc_rw".
xhc_dba=> create t000(id bigint,id2 serial primary key);
xhc_dba=> create table t000(id bigint,id2 serial primary key);
CREATE TABLE
xhc_dba=>
注2
xhc_dba=> c
psql (9.5.2, server 9.4.10)
You are now connected to database "xhc_dba" as user "xhc_rw".
xhc_dba=> d
List of relations
Schema | Name | Type | Owner
--------+--------------+----------+----------
public | t000 | table | xhc_rw
xhc_dba=> drop table t000;
虽然回收了xhc_rw的create权限，但是xhc_rw对以前建的表还是有ddl，权限的
注3
hc_dba=> c
psql (9.5.2, server 9.4.10)
You are now connected to database "xhc_dba" as user "xhc_test".
xhc_dba=> dn
List of schemas
Name | Owner
--------+----------
public | xhc_test
xhc_dba=> d
Schema | Name | Type | Owner
--------+-----------+----------+----------
public | t11 | table | xhc_rw
xhc_dba=> alter table t11 owner to xhc_test;
ALTER TABLE
xhc_dba=> alter table t11 owner to xhc_rw;
ERROR: permission denied for schema public
因为回收了所有用户的create权限，所以表的所属权是不可逆的，原来属于xhc_rw的表改成xhc_test之后就不能再改回来了
要想以后xhc_rw对不属于自己的表也有读写权限需要执行以下4句
grant select,insert,update,delete on all tables in schema public to xhc_rw;
WARNING: no privileges were granted for “test” —因为test表本来就属于xhc_rw用户，所以会有警告，如果把test 表owner改成xhc_test就不会有警告了
xhc_dba=> grant select,usage on all sequences in schema public to xhc_rw;
GRANT
xhc_dba=> alter default privileges in schema public grant select,update,delete,insert on tables to xhc_rw;
ALTER DEFAULT PRIVILEGES
xhc_dba=> alter default privileges in schema public grant select,usage on sequences to xhc_rw;
ALTER DEFAULT PRIVILEGES