Re: [PING] fallocate() causes btrfs to never compress postgresql files

On Fri, Jul 11, 2025 at 12:45 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
wrote:

> On Fri, Jul 11, 2025 at 5:39 AM Dimitrios Apostolou <jimis(at)gmx(dot)net> wrote:
> > > I applied the patch on PostgreSQL v17 and am testing it now. I chose
> > > ftruncate method and I see ftruncate in action using strace while doing
> > > pg_restore of a big database. Nothing unexpected has happened so far.
> I also
> > > verified that files are being compressed, obeying Btrfs's mount option
> > > compress=zstd.
> > >
> > > Thanks for the patch! What are the odds of commiting it to v17?
> >
> > Ping. :-)
> > Patch behaves good for me. Any chance of applying it and backporting it?
>
> Yeah, this seems to make sense, as it is a pretty bad regression for
> people who are counting on BTRFS compression for their large database.
> Not so sure about the threshold bit -- I'd probably leave that out of
> the backport in the interest of stable branch-minimalism. Anyone have
> any better ideas, better naming, or objections?
>

Not just to throw a wrench in there, but... Should this perhaps be a
tablespace option? ISTM having different filesystems for them is a good
reason to use tablespaces in the first place, and then being able to pick
different options...

--
Magnus Hagander
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