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From: Ellen Allhatatlan <[email protected]>
To: Rob Sargent <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: MVCC and all that...
Date: Tue, 9 Sep 2025 18:31:05 +0100
Message-ID: <CAMLfE0PbYk4WcXDydLJBaavtiimU=aMUKkyEHdC6izKKkHgP5g@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAMLfE0MAVH5YORs0OKmD=fFWH9EtuNsnhViti=+hkp3Kbz-Gfw@mail.gmail.com>
	<[email protected]>

> > In part 1. Differences in MVCC implementation - he's saying that "It’s
> > not that the PostgreSQL implementation of MVCC is bad — it’s just
> > fundamentally different"

> It is written by someone @firebirdsql.org so one assumes a few grains of salt necessary.


I know - but the guy does stress that he's not knocking PostgreSQL,
just that there are differences.

However, it *_was_* my understanding that MVCC was implemented
similarly in PostgreSQL and Firebird - PG has VACUUM and FB has SWEEP.
Why would FB need SWEEP if it didn't have to clear up after
transactions - a problem that apparently doesn't affect Oracle/MySQL?

Oracle and MySQL (InnoDB) implement a different model (as does
Orioledb IIUC) where there's are UNDO/REDO logs.

So, my question is: Is FB's MVCC implementation fundamentally
different from that of PG or have I mixed things up?

Thanks for your input.

-- 

El!

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