Re: Possibility to disable `ALTER SYSTEM`

On Mon, Mar 18, 2024 at 7:12 AM Jelte Fennema-Nio <postgres@jeltef.nl> wrote:
>
> On Mon, 18 Mar 2024 at 13:57, Robert Haas <robertmhaas@gmail.com> wrote:
> > I would have been somewhat inclined to find an existing section
> > of postgresql.auto.conf for this parameter, perhaps "platform and
> > version compatibility".
>
> I tried to find an existing section, but I couldn't find any that this
> new GUC would fit into naturally. "Version and Platform Compatibility
> / Previous PostgreSQL Versions" (the one you suggested) seems wrong
> too. The GUCs there are to get back to Postgres behaviour from
> previous versions. So that section would only make sense if we'd turn
> enable_alter_system off by default (which obviously no-one in this
> thread suggests/wants).
>
> If you have another suggestion for an existing category that we should
> use, feel free to share. But imho, none of the existing ones are a
> good fit.

+1 on Version and Platform Compatibility. Maybe it just needs a new
subsection there? This is for compatibility with a "deployment
platform". The "Platform and Client Compatibility" subsection has just
one entry, so a new subsection with also just one entry seems
defensible, maybe just "Deployment Compatibility"? I think it's also
plausible that there will be other similar settings for managed
deployments in the future.

> > Even if that is what we're going to do, do we want to call them "guard
> > rails"? I'm not sure I'd find that name terribly clear, as a user.
>
> If anyone has a better suggestion, I'm happy to change it.

No better suggestion at the moment, but while I used the term to
explain the feature, I also don't think that's a great official name.
For one thing, the section could easily be misinterpreted as guard
rails for end-users who are new to Postgres. Also, I think it's more
colloquial in tone than Postgres docs conventions.

Further, I think we may want to change the GUC name itself. All the
other GUCs that start with enable_ control planner behavior:

maciek=# select name from pg_settings where name like 'enable_%';
              name
--------------------------------
 enable_async_append
 enable_bitmapscan
 enable_gathermerge
 enable_hashagg
 enable_hashjoin
 enable_incremental_sort
 enable_indexonlyscan
 enable_indexscan
 enable_material
 enable_memoize
 enable_mergejoin
 enable_nestloop
 enable_parallel_append
 enable_parallel_hash
 enable_partition_pruning
 enable_partitionwise_aggregate
 enable_partitionwise_join
 enable_presorted_aggregate
 enable_seqscan
 enable_sort
 enable_tidscan
(21 rows)

Do we really want to break that pattern?