Re: Refactoring the checkpointer's fsync request queue

Hi,

On 2019-02-23 11:59:04 +1300, Thomas Munro wrote:
> On Sat, Feb 23, 2019 at 11:48 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > > Yeah I suggested dynamic registration to avoid the problem that eg
> > > src/backend/storage/sync.c otherwise needs to forward declare
> > > md_tagtopath(), undofile_tagtopath(), slru_tagtopath(), ..., or maybe
> > > #include <storage/md.h> etc, which seemed like exactly the sort of
> > > thing up with which you would not put.
> >
> > I'm not sure I understand. If we have a few known tag types, what's the
> > problem with including the headers with knowledge of how to implement
> > them into sync.c file?
>
> Typo in my previous email: src/backend/storage/file/sync.c was my
> proposal for the translation unit holding this stuff (we don't have .c
> files directly under storage). But it didn't seem right that stuff
> under storage/file (things concerned with files) should know about
> stuff under storage/smgr (md.c functions, higher level smgr stuff).
> Perhaps that just means it should go into a different subdir, maybe
> src/backend/storage/sync/sync.c, that knows about files AND smgr
> stuff, or perhaps I'm worrying about nothing.

I mean, if you have a md_tagtopath and need its behaviour, I don't
understand why a local forward declaration changes things? But I also
think this is a bit of a non-problem - the abbreviated path names are
just a different representation of paths, I don't see a problem of
having that in sync.[ch], especially if we have the option to also have
a full-length pathname variant if we ever need that.

Greetings,

Andres Freund