Re: Basic Questions about PostgreSQL.

On Wed, 2021-09-15 at 05:10 +0000, A Z wrote:
> -In PostgreSQL, what is the difference between Roles, Groups, and
> Policies exactly? What are they each, how do they relate to one
> another, and which one(s) can be assigned to another?
> 
> -Is there a simple, immediate, straightforward way to temporarily
> disable PostgreSQL database
> use of all other users, except development users, or in fact just one
> user (one developer, yourself)
> so that maintenance on the data or the data model may be performed?
> 

Read
https://www.postgresql.org/docs/13/app-postgres.html#id-1.9.5.14.6.5

about single user mode.
You shut down the cluster and run psql in single user mode.
After you quit out of single user mode, restart.

HTH,
Rob