Re: BUG #19761: btree_gist: "cannot subtract infinite dates" when inserting 'infinity' into a GiST index on date

On Mon, Oct 26, 2026 at 9:40 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> I think this is not there yet. An important behavior of the
> corresponding code for float8 (float_penalty_num_impl()) is that
> it makes the distance between two same-sign infinity values be zero,
> not infinity. This is mathematically wrong but we must do it for
> indexing purposes, else inserting multiple infinities will end up
> splitting each infinity onto its own index page when we want all
> identical infinities to pack onto as few index pages as possible.
>
> BTW, while checking this I happened to notice that
> gbt_float8_dist has a variant of the same problem:
>
> r = arg1 - arg2;
> if (unlikely(isinf(r)) && !isinf(arg1) && !isinf(arg2))
> float_overflow_error();
>
> I don't think we want an error thrown there either;
> returning the infinite distance (or DBL_MAX?) seems better.
>

Thanks a lot for the review, Tom. I'll be able to work on this in a
couple of weeks. Will look into it in detail and send the updated
patch at that time.

Regards,
Nitin Motiani
Google