Re: [PATCH] Stop ALTER SYSTEM from making bad assumptions

Greetings,

On Fri, Aug 2, 2019 at 18:27 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> > There seems to be a consensus that this this not a pg_basebackup issue
> > (i.e. duplicate values don't make the file invalid), and it should be
> > handled in ALTER SYSTEM.
>
> Yeah. I doubt pg_basebackup is the only actor that can create such
> situations.
>
> > The proposal seems to be to run through the .auto.conf file, remove any
> > duplicates, and append the new entry at the end. That seems reasonable.
>
> +1

I disagree that this should only be addressed in alter system, as I’ve said
before and as others have agreed with. Having one set of code that can be
used to update parameters in the auto.conf and then have that be used by
pg_basebackup, alter system, and external tools, is the right approach.

The idea that alter system should be the only thing that doesn’t just
append changes to the file is just going to lead to confusion and bugs down
the road.

As I said before, an alternative could be to make alter system simply
always append and declare that to be the way to update parameters in the
auto.conf.

> There was a discussion whether to print warnings about the duplicates. I
> > personally see not much point in doing that - if we consider duplicates
> > to be expected, and if ALTER SYSTEM has the license to rework the config
> > file any way it wants, why warn about it?
>
> Personally I agree that warnings are unnecessary.

And at least Magnus and I disagree with that, as I recall from this
thread. Let’s have a clean and clear way to modify the auto.conf and have
everything that touches the file update it in a consistent way.

Thanks,

Stephen