Re: Renaming of pg_xlog and pg_clog

* Magnus Hagander (magnus@hagander.net) wrote:
> On Fri, Oct 14, 2016 at 4:35 AM, Stephen Frost <sfrost@snowman.net> wrote:
> > * Peter Eisentraut (peter.eisentraut@2ndquadrant.com) wrote:
> > > On 10/12/16 11:22 AM, Tom Lane wrote:
> > > > The main problem we're trying to fix here is people thinking that
> > > > something with "log" in the name contains discardable data.  Just
> > > > relocating the directory without renaming it won't improve that.
> > >
> > > I think it would help if we moved it to something like
> > > "internal/pg_xlog" and "internal/pg_clog".  Keep the name but move it
> > > out of sight.
> >
> > I disagree that this will materially help with the issue.
> >
> > > We have a tool called pg_xlogdump in the standard installation.  initdb
> > > has an option --xlogdir, pg_basebackup has --xlog and others.  Renaming
> > > the xlog directory would make this all a bit confusing, unless we're
> > > prepared to rename the programs and options as well.
> >
> > pg_xlogdump is not a user-facing tool, frankly, so I don't believe we
> > should be terribly concerned about either leaving it named as-is or
> > renaming it.  I agree that we should consider adding alternative names
> > to the options for initdb and pg_basebackup.
>
> Ugh. Changing the names of those options are probably going to break a
> *lot* of things, a lot more than changing the names of the directories. Is
> it really worth doing that? Especially if we are even more clear that
> people should not be touching those directories in the first place.

I would point out that I said "adding alternative names", not
"change/remove the existing options."

That said, while I like the general idea of "make everything referring
to transaction log/write-ahead xlog/xlog/wal/whatever refer in the same
way", I'm not sure that it's a really pressing issue or that changing
the name of the directory should drive those other changes.

> Those are just the tip of the iceberg. We do use the term xlog in a lot of
> places (almost as many as wal, but that's a different problem)

True, and yes, we should consider the places that already talk about
"wal", but, overall, I believe we can take this one step at a time and
don't have to do everything all at once simply because we're changing
the directory name.  We're not changing what it *is*, after all.