Re: Disallow redundant indexes

Hi, Greg and David

Thank you for your feedback.

On Thu, 24 Apr 2025 at 08:26, Greg Sabino Mullane <htamfids(at)gmail(dot)com> wrote:
> On Thu, Apr 24, 2025 at 7:31 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> On Thu, 24 Apr 2025 at 21:27, Japin Li <japinli(at)hotmail(dot)com> wrote:
> > I propose that PostgreSQL prevent redundant index creation by:
>
>
> In any case, who are we to define what a duplicate index is?
>

You're absolutely right. Defining a duplicate index is indeed simpler than
I initially described.

> I think this part is easier than you make it sound: everything (except the name) is exactly the same as an existing
> index. That's the 99% case we are trying to catch here.
>

As Greg pointed out, if everything except the name is identical to an existing
index, it should be considered a duplicate in most cases (the 99% case).
This is precisely the scenario I'm aiming to prevent.

> I've had this idea before, and even wrote a quick POC at one point, but I had it simply throw a warning rather than an
> error. That avoids the need for any GUC, which I agree is not a good idea. And it still allows people to create a
> duplicate index if they really want to.
>

I also appreciate your suggestion regarding the GUC parameter. You've
convinced me that a warning might be a more appropriate approach. A warning
would still alert users to the potential issue of creating a redundant index,
while allowing them to proceed if they have a specific reason to do so.

--
Regrads,
Japin Li