> To be able to select from a table you need

> * CONNECT

> * USAGE

> * SELECT

Isn't LOGIN (https://www.postgresql.org/docs/16/role-attributes.html) also needed?

  Only roles that have the LOGIN attribute can be used as the initial role name for a database connection

You can log in and then change your role (if you permissions) with SET ROLE NEW_USER;

We managed to kludge our way to defaulting to read only, then using set role to do writes if you need to.

Good point. Connecting to the Cluster is indeed actually a 4th layer.

There you do need user with LOGIN, valid password & SSL.

> What makes it complex is that there are 3 layers of objects (Database, Schema, Tables) and also implicit grants given to DB object owners

The main privileges systems includes Columns, as well as Databases/Schemas/Tables. You can SELECT from a table if you have been granted SELECT on the table, or if you have been granted it on the specific columns used in your query. ("A user may perform SELECT, INSERT, etc. on a column if they hold that privilege for either the specific column or its whole table. Granting the privilege at the table level and then revoking it for one column will not do what one might wish: the table-level grant is unaffected by a column-level operation." [1])

There's also a system of Row Security Policies [2].

[1]: https://www.postgresql.org/docs/current/sql-grant.html

[2]: https://www.postgresql.org/docs/current/ddl-rowsecurity.html

I've seen funny things happen when developers think their GRANT is doing what ALTER DEFAULT PRIVILEGES does, and a day later break production because their user doesn't have access to the new tables.

What do you mean exactly?

If roles have INHERIT, then doing the following works, no?

* Role A creates table * GRANT A TO B; * ROLE B can read from table just like A can.

Also if Role A creates new table, Role B can read that too no?

Remove any "if" from your comment and it seems like you understood what would fail! There's more ways to make misunderstanding grant vs default privileges will create issues as well.

Then I would argue for trying to centrally ensure that all roles have INHERIT in your DBs. :thinking:

Doing ALTER DEFAULT PRIVILEGES could be another future footgun of it's own.

I think you probably don’t want the application user to inherit from the superuser you may use for migrations since some migrations require a superuser.

IMO, the permission management of the MS SQL Server is the best one around. It gets all the basics right, without any big issue. Other DBMS should copy it, or use it as a starting point if they want to go further (and there is plenty of stuff to improve on it).

TLDR, the container objects and the contained ones all share the same kind of permissions. Permissions of the container are applied to the contained unless explicitly changed.

So, if you grant select on the schema dbo to a, a will get select on all tables there. If you want to remove some table, you revoke the select on that specific table. And there is both metadata to discover where a specific privilege comes from and specific commands that edit the privileges on a specific level.