Re: WAL_LOG CREATE DATABASE strategy broken for non-standard page layouts

On Mon, May 13, 2024 at 10:53 AM Matthias van de Meent
<boekewurm+postgres@gmail.com> wrote:
> It's not inconceivable that this will significantly increase WAL
> volume, but I think we should go for correctness rather than fastest
> copy.

I don't think we can afford to just do this blindly for the sake of a
hypothetical non-core AM that uses nonstandard pages. There must be
lots of cases where the holes are large, and where the WAL volume
would be a multiple of what it is currently. That's a *big*
regression.

> If we went with fastest copy, we'd better just skip logging the
> FSM and VM forks because we're already ignoring the data of the pages,
> so why not ignore the pages themselves, too? I don't think that holds
> water when we want to be crash-proof in CREATE DATABASE, with a full
> data copy of the template database.

This seems like a red herring. Either assuming standard pages is a
good idea or it isn't, and either logging the FSM and VM forks is a
good idea or it isn't, but those are two separate questions.

--
Robert Haas
EDB: http://www.enterprisedb.com