Wondering about an ets:select_reverse equivalent for mnesia

[Bentheburrito]

Is your feature request related to a problem? Please describe.
ets has a select_reverse/1-3, which is the same as select/1-3 except it traverses an ordered_set table backwards. There doesn't seem to be an equivalent for mnesia, only mnesia:select/1-4. Is there a particular reason/limitation for this, or has there simply been no need for it in the past?

Describe the solution you'd like
An mnesia:select_reverse/1-4 would be very useful to me, as I'd like the ability to traverse an ordered_set table in both directions.

Describe alternatives you've considered
mnesia does have an ets/1,2 which might work, but I think is undesirable since the given function is executed "in a raw context that is not protected by a transaction."

Additional context
I'm a new mnesia user, so apologies if I've missed something. If there is no technical reason why mnesia:select_reverse could not exist, I'd be happy to try to contribute it. I am more of an Elixir than Erlang dev though, so any guidance (outside of reading the contributor's guide of course) would be welcome :)

Thanks in advance!

[Mikaka27]

We're open to contributions regarding this, from quick look at the code I don't see any obvious limitations.
But you must know that adding this requires extending external backends as well.

So things like: https://github.com/aeternity/mnesia_rocksdb would need to be adapted as well (they would need to handle new callback).

[Bentheburrito]

Awesome! I'll take a look at implementing this when I get some time (hopefully later this month).

After I get a PR up for review, would opening an issue to note the new callback in the external backends' repositories suffice? I'm not familiar with the external backend landscape, so let me know if there are any other widely used ones that should be made aware (I see mnesia_rocksdb mentions mnesia_eleveldb)

[dgud]

You don't have to make that, just make sure it could work for them to add the functionality.