Re: Fix output of zero privileges in psql

On Sat, 2023-10-07 at 05:07 +0200, Erik Wienhold wrote:
> On 2023-10-06 22:32 +0200, Laurenz Albe write:
> > On Sun, 2023-09-17 at 21:31 +0200, Erik Wienhold wrote:
> > > I wrote a patch to change psql's display of zero privileges after a user's
> > > reported confusion with the psql output for zero vs. default privileges [1].
> > > Admittedly, zero privileges is a rare use case [2] but I think psql should not
> > > confuse the user in the off chance that this happens.
> > >
> > > [1] https://www.postgresql.org/message-id/efdd465d-a795-6188-7f71-7cdb4b2be031%40mtneva.com
> > > [2] https://www.postgresql.org/message-id/31246.1693337238%40sss.pgh.pa.us
> >
> > Reading that thread, I had the impression that there was more support for
> > honoring "\pset null" rather than unconditionally displaying "(none)".
>
> For example with your patch applied:
>
>         create table t1 (a int);
>         create table t2 (a int);
>         create table t3 (a int);
>
>         revoke all on t2 from :USER;
>
>         \pset null <NULL>
>         \dp t1|t2|t3
>                                     Access privileges
>          Schema | Name | Type  | Access privileges | Column privileges | Policies
>         --------+------+-------+-------------------+-------------------+----------
>          public | t1   | table | <NULL>            |                   |
>          public | t2   | table |                   |                   |
>          public | t3   | table | <NULL>            |                   |
>         (3 rows)
>
> Instead of only displaying the zero privileges with my patch and default
> \pset null:
>
>         \pset null ''
>         \dp t1|t2|t3
>                                     Access privileges
>          Schema | Name | Type  | Access privileges | Column privileges | Policies
>         --------+------+-------+-------------------+-------------------+----------
>          public | t1   | table |                   |                   |
>          public | t2   | table | (none)            |                   |
>          public | t3   | table |                   |                   |
>         (3 rows)
>
> I guess if most tables have any non-default privileges then both
> solutions are equally good.

It is a tough call.

For somebody who knows PostgreSQL well enough to know that default privileges are
represented by NULL values, my solution is probably more appealing.

It seems that we both had the goal of distinguishing the cases of default and
zero privileges, but for a beginner, both versions are confusing. better would
probably be

                             Access privileges
  Schema | Name | Type  | Access privileges | Column privileges | Policies
 --------+------+-------+-------------------+-------------------+----------
  public | t1   | table | default           | default           |
  public | t2   | table |                   | default           |
  public | t3   | table | default           | default           |

The disadvantage of this (and the advantage of my proposal) is that it might
confuse experienced users (and perhaps automated tools) if the output changes
too much.

> > The simple attached patch does it like that.  What do you think?
>
> LGTM.

If you are happy enough with my patch, shall we mark it as ready for committer?
Or do you want to have a stab at something like I suggested above?

Yours,
Laurenz Albe