创建用户及指定密码：
CREATE USER readonly WITH ENCRYPTED PASSWORD 'ropass';
设置用户默认事务只读：
alter user readonly set default_transaction_read_only=on;
赋予用户权限，查看public模式下所有表：
GRANT USAGE ON SCHEMA public to readonly;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readonly;
赋予用户连接数据库权限：
GRANT CONNECT ON DATABASE foo to readonly;
切换到指定数据库：
\c foo
赋予用户表、序列查看权限：
GRANT USAGE ON SCHEMA public to readonly;
GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO readonly;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readonly;