Re: Renaming of pg_xlog and pg_clog

On Fri, Oct 14, 2016 at 11:48 AM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:

> * Magnus Hagander (magnus(at)hagander(dot)net) wrote:
> > On Fri, Oct 14, 2016 at 4:35 AM, Stephen Frost <sfrost(at)snowman(dot)net>
> wrote:
> > > * Peter Eisentraut (peter(dot)eisentraut(at)2ndquadrant(dot)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."
>

Oh, I missed that. Thanks for clarifying :)

> 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.
>

Agreed.

> > 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.
>

Yeah, I think if we aim to fix everything at once, we'll get nothing done.
That old saying of not letting perfection getting in the way of progress
applies.

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/