From: | Melanie Plageman <melanieplageman(at)gmail(dot)com> |
---|---|
To: | Daniel Gustafsson <daniel(at)yesql(dot)se> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Re: Add LSN <-> time conversion functionality |
Date: | 2024-06-28 22:09:23 |
Message-ID: | CAAKRu_b-X_BDieA23r2vq_nzYcPvvs22MDpiZw_y8cS7yGFk7A@mail.gmail.com |
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Lists: | pgsql-hackers |
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
Attachment | Content-Type | Size |
---|---|---|
v5-0002-Add-LSNTimeStream-for-converting-LSN-time.patch | text/x-patch | 10.5 KB |
v5-0004-Bgwriter-maintains-global-LSNTimeStream.patch | text/x-patch | 1.6 KB |
v5-0001-Record-LSN-at-postmaster-startup.patch | text/x-patch | 2.6 KB |
v5-0005-Add-time-LSN-translation-functions.patch | text/x-patch | 6.6 KB |
v5-0003-Add-LSNTimeStream-to-PgStat_WalStats.patch | text/x-patch | 1.8 KB |
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