Re: Add LSN <-> time conversion functionality

On Wed, Jun 26, 2024 at 10:04 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
>
> I've implemented these review points in the attached v4.

I realized the docs had a compilation error. Attached v5 fixes that as
well as three bugs I found while using this patch set more intensely
today.

I see Michael has been working on some crash safety for stats here
[1]. I wonder if that would be sufficient for the LSNTimeStream. I
haven't examined his patch functionality yet, though.

I also had an off-list conversation with Robert where he suggested I
could perhaps change the user-facing functions for estimating an
LSN/time conversion to instead return a floor and a ceiling -- instead
of linearly interpolating a guess. This would be a way to keep users
from misunderstanding the accuracy of the functions to translate LSN
<-> time. I'm interested in what others think of this.

I like this idea a lot because it allows me to worry less about how I
decide to compress the data and whether or not it will be accurate for
use cases different than my own (the opportunistic freezing
heuristic). If I can provide a floor and a ceiling that are definitely
accurate, I don't have to worry about misleading people.

- Melanie

[1] https://www.postgresql.org/message-id/ZnEiqAITL-VgZDoY%40paquier.xyz