Re: Temporary file access API

Antonin Houska <ah(at)cybertec(dot)at> wrote:

> Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> > On Tue, Apr 12, 2022 at 5:30 AM Antonin Houska <ah(at)cybertec(dot)at> wrote:
> > > Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> > > > On Mon, Apr 11, 2022 at 4:05 AM Antonin Houska <ah(at)cybertec(dot)at> wrote:
> > > > > There are't really that many kinds of files to encrypt:
> > > > >
> > > > > https://wiki.postgresql.org/wiki/Transparent_Data_Encryption#List_of_the_files_that_contain_user_data
> > > > >
> > > > > (And pg_stat/* files should be removed from the list.)
> > > >
> > > > This kind of gets into some theoretical questions. Like, do we think
> > > > that it's an information leak if people can look at how many
> > > > transactions are committing and aborting in pg_xact_status? In theory
> > > > it could be, but I know it's been argued that that's too much of a
> > > > side channel. I'm not sure I believe that, but it's arguable.
> > >
> > > I was referring to the fact that the statistics are no longer stored in files:
> > >
> > > https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=5891c7a8ed8f2d3d577e7eea34dacff12d7b6bbd
> >
> > Oh, yeah, I agree with that.
>
> I see now that the statistics are yet saved to a file on server shutdown. I've
> updated the wiki page.
>
> Attached is a new version of the patch, to evaluate what the API use in the
> backend could look like. I haven't touched places where the file is accessed
> in a non-trivial way, e.g. lseek() / fseek() or pg_pwrite() / pg_pread() is
> called.

Rebased patch set is attached here, which applies to the current master.

(A few more opportunities for the new API implemented here.)

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