Re: POC: Cleaning up orphaned files using undo logs

Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:

> On Fri, Sep 17, 2021 at 9:50 PM Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
> >
> > > On Tue, Sep 14, 2021 at 10:51:42AM +0200, Antonin Houska wrote:
> >
> > * What happened with the idea of abandoning discard worker for the sake
> > of simplicity? From what I see limiting everything to foreground undo
> > could reduce the core of the patch series to the first four patches
> > (forgetting about test and docs, but I guess it would be enough at
> > least for the design review), which is already less overwhelming.
> >
>
> I think the discard worker would be required even if we decide to
> apply all the undo in the foreground. We need to forget/remove the
> undo of committed transactions as well which we can't remove
> immediately after the commit.

I think I proposed foreground discarding at some point, but you reminded me
that the undo may still be needed for some time even after transaction
commit. Thus the discard worker is indispensable.

What we can miss, at least for the cleanup of the orphaned files, is the *undo
worker*. In this patch series the cleanup is handled by the startup process.

--
Antonin Houska
Web: https://www.cybertec-postgresql.com