Re: Proposal to Enable/Disable Index using ALTER INDEX

On Wed, Oct 9, 2024 at 4:19 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> On Wed, 9 Oct 2024 at 20:07, Shayon Mukherjee <shayonj(at)gmail(dot)com> wrote:
> > [thinking…] Unless - we try to do support both a GUC and the ALTER INDEX ENABLE/DISABLE grammar + isdisabled attribute on pg_index?
>
> I just wanted to explain my point of view on this. This is my opinion
> and is by no means authoritative.
>
> I was interested in this patch when you proposed it as an ALTER INDEX
> option. I know other committers seem interested, but I personally
> don't have any interest in the GUC option. I think the reason I
> dislike it is that it's yet another not even half-baked take on
> planner hints (the other one being enable* GUCs). I often thought that
> if we ever did planner hints that it would be great to have multiple
> ways to specify the hints. Ordinarily, I'd expect some special comment
> type as the primary method to specify hints, but equally, it would be
> nice to be able to specify them in other ways. e.g. a GUC to have them
> apply to more than just 1 query. Useful for things such as "don't use
> index X".

+1. A GUC can be done as a contrib module using existing hooks, and I
think that's already been done outside of core, perhaps multiple
times. That certainly doesn't mean we CAN'T add it as an in-core
feature, but I do think "yet another not even half-baked take on
planner hints" is a fair description. What I would personally like to
see is for us to ship one or possibly more than one contrib module
that let people do hint-like things in useful ways, and this could be
a part of that. But I think we need better infrastructure for
controlling the planner behavior first, hence the "allowing extensions
to control planner behavior" thread.

--
Robert Haas
EDB: http://www.enterprisedb.com