Re: GetRelationPath() vs critical sections

On Thu, Feb 20, 2025 at 12:40:57PM -0500, Andres Freund wrote:
> On 2025-02-20 14:00:10 +1300, Thomas Munro wrote:
> > On Wed, Feb 19, 2025 at 3:35 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > > After thinking about this for an embarassingly long time, I think there's
> > > actually a considerably better answer for a case like this: A function that
> > > returns a fixed-length string by value:
> > >
> > > - Compilers can fairly easily warn about on-stack values that goes out of
> > > scope
> > >
> > > - Because we don't need to free the memory anymore, some code that that
> > > previously needed to explicitly free the memory doesn't need to anymore
> > > (c.f. AbortBufferIO()).
> > >
> > > - The max lenght isn't that long, so it's actually reasonably efficient,
> > > likely commonly cheaper than psprintf.
> >
> > I like it!

Works for me.

> Unfortunately I had to exclude "relpath" as there are just too many
> independent hits, due to the python function of the same name. For
> relpathperm(), relpathbackend(), GetRelationPath() there looks to be just
> fincore.

PGXN has few hits, and some of these are false positives or otherwise
irrelevant:

$ grep -re '[^.]\(relpath[a-z]*\|GetRelationPath\)(' | sed 's/-[^:]*/:/'|sort -u
db2_fdw::extern char *GetRelationPath(Oid dbNode, Oid spcNode, Oid relNode,
jsoncdc:: pub fn GetRelationPath(dbNode: Oid, spcNode: Oid, relNode: Oid,
openbarter:: path = relpath(frame.f_code.co_filename, refdir) # relative to refdir
pg_bulkload::#define relpath(rnode, forknum) relpath((rnode))
pg_bulkload:: fname = relpath(bknode, MAIN_FORKNUM);
pg_bulkload:: fname = relpath(rnode, MAIN_FORKNUM);
pg_repack::#define relpath(rnode, forknum) relpath((rnode))
plv8:: def _to_relpath(self, abspath, _):
plv8:: def _to_relpath(self, abspath, test_root):
plv8:: yield self._to_relpath(abspath, test_root)
tblsize_nolock:: relationpath = relpath(*rfn);

> Which makes me think it's not worth having a backward compatible interface?

Agreed. Even if 100% of those matches had to change, that's below standard
level of breakage for a major release.