Re: Bug in nbtree optimization to skip > operator comparisons (or < comparisons in backwards scans)

Pavel,

On Mon, Dec 25, 2023 at 8:32 PM Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com> wrote:
> I've reviewed both patches:
> 0001 - is a pure refactoring replacing argument transfer from via struct member to transfer explicitly as a function argument. It's justified by the fact firstPage is localized only to several places. The patch looks simple and good enough.
>
> 0002:
> continuescanPrechecked is semantically much better than previous requiredMatchedByPrecheck which confused me earlier. Thanks!
>
> From the new comments, it looks a little bit hard to understand who does what. Semantics "if caller told" in comments looks more clear to me. Could you especially give attention to the comments:
>
> "If they wouldn't be matched, then the *continuescan flag would be set for the current item and the last item on the page accordingly."
> "If the key is required for the opposite direction scan, we need to know there was already at least one matching item on the page. For those keys."
>
> > Prechecking the value of the continuescan flag for the last item on the
> >+ * page (according to the scan direction).
> Maybe, in this case, it would be more clear like: "...(for backwards scan it will be the first item on a page)"
>
> Otherwise the patch 0002 looks like a good fix for the bug to be pushed.

Thank you for your review. I've revised comments to meet your suggestions.

------
Regards,
Alexander Korotkov