Re: Should pg_current_wal_location() become pg_current_wal_lsn()

At Sat, 15 Apr 2017 12:56:32 -0400, Robert Haas <robertmhaas(at)gmail(dot)com> wrote in <CA+TgmoZjDo9ckxf6aYrqyMoiSw5yfBB2gpMbrBtE9zr==uczhw(at)mail(dot)gmail(dot)com>
> On Fri, Apr 14, 2017 at 6:52 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
> >> If we're talking about making things easier to understand, wouldn't a
> >> random user rather know what a WAL "location" is instead of a WAL "LSN"?
> >
> > I wouldn't object to standardizing on "location" instead of "lsn" in the
> > related function and column names. What I don't like is using different
> > words for the same thing.
>
> The case mentioned in the subject of this thread has been using the
> word "location" since time immemorial. It's true that we've already
> renamed it (xlog -> wal) in this release, so if we want to standardize
> on lsn, now's certainly the time to do it. I'm worried that
> pg_current_wal_lsn() is an identifier composed almost entirely of
> abbreviations and therefore possibly just as impenetrable as
> qx_current_pfq_dnr(), but maybe we should assume that LSN is a term of
> art with which knowledgeable users are required to be familiar, much
> as we are doing for "WAL".
>
> It appears, from grepping the 9.6 version of pg_proc.h, that both lsn
> and location have some historical precedent.

I'd better to have replied here. The detail is in my reply on
another brandh of this thread.

https://www.postgresql.org/message-id/20170417.143937.232025253.horiguchi.kyotaro@lab.ntt.co.jp

After all, "location" seems better to me in user interface. We
could rename almost all of %lsn% names into %location% except
pg_lsn oprators as long as it doesn't become too long or complex.

One annoyance is the historical function pg_xlog_location_diff(),
which is currently just an alias of pg_lsn_mi. It is
substantially an operator, but 'pg_wal_lsn_diff()' is so far from
the historical name that it becomes totally useless.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center