CREATE USER readonly  WITH ENCRYPTED PASSWORD 'readonly';
GRANT USAGE ON SCHEMA public to readonly;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readonly;

-- repeat code below for each database:

GRANT CONNECT ON DATABASE foo to readonly;
\c foo
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;

感谢http://jamie.curle.io/creating-a-read-only-user-in-postgres/几个重要方面

如果任何人找到更短的代码，并且最好是能够对所有现有数据库执行此代码，额外的努力。