Create a list that contains the full sequence, then iterate over those two lists at once

Check if the items match, and return the first one that's not matching

Yeah, but I would need it to use 3 separate ranges of numbers, and I'm trying to keep it as skinny as possible, if at all possible.

Why 3?

Two

The list you're checking, and the list you're checking against

Alternatively, you can of course check if n+1 - 1 == 1

I'm basically making a new ID, and I want it to take the first value that's free so I can use that, rather than just adding 1 to the end of the list(which will be what happens if I don't find anything). I have 3 separate ranges of numbers that would need to be checked, depending on a value that's passed in. Does that make more sense? I know I'm not explaining the best.

Also these lists are around 100 million long, so making that separate full list would be pretty impractical. 😅

I wouldn't worry about taking up every possible ID, then, to be honest

No database engine does

They just keep track of the last ID and insert the next item at that plus one

Yeah, that's fair. I was just trying to save as much space as possible, I guess. Though, I doubt anyone will hit 100 million items in one database.

Thanks for the help!

check out free lists some time

Do you have a link?

https://en.m.wikipedia.org/wiki/Free_list#:~:text=A%20free%20list%20(or%20freelist,a%20pointer%20to%20the%20next.

the id stuff is captured in this blog https://skypjack.github.io/2019-02-14-ecs-baf-part-1/

Ok, I'll take a look in a little bit. Thanks!