public inbox for [email protected]  

help / color / mirror / Atom feed

From: Ellen Allhatatlan <[email protected]>
To: Merlin Moncure <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: MVCC and all that...
Date: Tue, 9 Sep 2025 18:57:30 +0100
Message-ID: <CAMLfE0MWqALMJ99dpFniZ1xknCgHj4ETPWro+Ry9awPUG1OKMw@mail.gmail.com> (raw)
In-Reply-To: <CAHyXU0yrwoEYia0mZhpjQLMdd-WXpWFM+Au1jXQpk3MtBvdogw@mail.gmail.com>
References: <CAMLfE0MAVH5YORs0OKmD=fFWH9EtuNsnhViti=+hkp3Kbz-Gfw@mail.gmail.com>
	<CAHyXU0yrwoEYia0mZhpjQLMdd-WXpWFM+Au1jXQpk3MtBvdogw@mail.gmail.com>

> Note: your link is wrong, corrected here:

Extra hyphen - sorry about and thanks for pointing it out!

> What the article is driving at is that postgres does not use rollback logs to handle updated records in the MVCC implementation.  There are absolutely performance tradeoffs in that decision and, if you do a lot of development against postgresql, those tradeoffs should influence how you design databases.  The author then cherry picked the 'worst case' case, large unconstrained updates.

Hmm... I was wondering about that - even though he stressed that there
was (paraphrasing) no right or wrong - just different design
decisions!

> The article is a bit of a cheezy dig on postgres.  Another example is the complaint about autonomous transactions with another cherry picked example to make postgres look back. In the real world, these would not matter much, and can be worked around (if you want to see my take on how to deal with it, see here: https://github.com/leaselock/pgasync).

OK - so, I was wrong in my original assumption that somehow (and it
wasn't simply because of the phraseology - sweep vs vacuum) I thought
that PG and FB had a similar MVCC implementation vs. Oracle and MySQL
(InnoDB) (and OrioleDB). I'll do a deep dive into their docco and see
what they actually do! I'm actually very interested in the
benchmarking side of database technology - but I do know the old adage
- there are lies, damned lies, statistics and *_then_* there are
database benchmarks (as seen with the link I posted!).

Thanks for your input.

Best regards,


El!

> merlin

view thread (21+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected]
  Subject: Re: MVCC and all that...
  In-Reply-To: <CAMLfE0MWqALMJ99dpFniZ1xknCgHj4ETPWro+Ry9awPUG1OKMw@mail.gmail.com>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox