创建数据库bbb且owner为用户b：
postgres9.6@[local]:5432 postgres# create database bbb owner b;
CREATE DATABASE
Time: 259.099 ms
默认情况下使用用户c也可以连接数据库bbb：
postgres9.6@[local]:5432 postgres# \c bbb c
You are now connected to database "bbb" as user "c".
回收public的connect on database bbb权限：
c@[local]:5432 bbb# \c postgres postgres9.6
You are now connected to database "postgres" as user "postgres9.6".
postgres9.6@[local]:5432 postgres# revoke connect on database bbb from public;
REVOKE
Time: 2.088 ms
此时用户c没有了连接数据库bbb的权限：
postgres9.6@[local]:5432 postgres# \c bbb c
FATAL: permission denied for database "bbb"
DETAIL: User does not have CONNECT privilege.
Previous connection kept
但bbb数据库的owner用户b可以连接数据库：
postgres9.6@[local]:5432 postgres# \c bbb b
You are now connected to database "bbb" as user "b".
b@[local]:5432 bbb#
此种情况下超级用户也可以连接该数据库：
b@[local]:5432 bbb# \c bbb postgres9.6
You are now connected to database "bbb" as user "postgres9.6".
postgres9.6@[local]:5432 bbb#
postgres9.6@[local]:5432 bbb# \du
List of roles
Role name | Attributes | Member of
-------------+------------------------------------------------------------+-----------
a | | {}
b | | {}
c | | {}
postgres9.6 | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
另外一种方法：从pg_hba.conf中限定：
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all 127.0.0.1/32 trust
...
#
host all all 0.0.0.0/0 md5
补充：Postgres限制每个用户只能连接指定数量的session，防止服务器资源紧张
限制每个用户只能连接指定数量的session，防止服务器资源紧张
（1）创建测试用户test:
highgo=#create user test;
CREATEROLE
highgo=#\du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+----------
highgo | Superuser, Create role, Create DB, Replication | {}
test | | {}
（2）设置仅允许用户test使用一个连接
highgo=#ALTER ROLE test CONNECTION LIMIT 1;
ALTERROLE
（3）在session 1中使用test用户连接highgo数据库
highgo=>\c highgo test
Youare now connected to database "highgo" as user "test".
highgo=>
（4）在session 2中也使用test用户连接highgo数据库，会出现如下错误：
highgo=#\c highgo test
致命错误: 由角色"test"发起的连接太多了
Previousconnection kept
（5）查询用户test链接限制
highgo=>SELECT rolconnlimit FROM pg_roles WHERE rolname = 'test';
rolconnlimit
--------------
1
(1row)
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。如有错误或未考虑完全的地方，望不吝赐教。
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