Peter Eisentraut wrote:

> You really have (at least) three options here:
> 1. Rename nothing
> 2. Rename directory only
> 3. Rename everything

I vote for 1) as I believe the renaming will create more confusion
than it's worth, not even considering the renaming of functions
and views.

What if we look at the change from the pessimistic angle?
An example of confusion that the change would create:
a lot of users currently choose pg_wal for the destination
directory of their archive command. Less-informed users
that set up archiving and/or log shipping in PG10 based on
advice online from previous versions will be fairly
confused about the missing pg_xlog, and the fact that the
pg_wal directory they're supposed to create already exists.

Also googling for pg_wal, I'm finding food for thought like this
IBM technote:
which recommends to 
"Remove all files under /var/lib/pgsql/9.0/data/pg_wal/"
and also calls that directory the "write-ahead log directory"
which is quite confusing because apparently it's the destination of
their archive command.

This brings the question: what about the people who will delete
their pg_wal (ex-pg_xlog) when they face a disk-full condition and
they mix up in their mind the archive directory and the WAL directory?
It's hard to guess how many could make that mistake but I don't see
why it would be less probable than confusing pg_xlog and pg_log.
At least the contents of the latter directories look totally
different, contrary to the wal directory versus wal archive.

Also, what about the users who are helped currently by
the fact that "pg_xlog" is associated at the top of google results
to good articles that explain what it is, why it fills up and what
to do about it? By burying the name "pg_xlog" we're also loosing that
connection, and in the worst case making worse the problem we
wanted to help with.

There's also the disruption in existing backup scripts that directly
reference pg_xlog. Obviously these scripts are critical, and there's
something weird in breaking that intentionally. The motivation of the
breakage is likely to be felt as frivolous and unfair to those people who
are adversely impacted by the change, even if the part of not
reading the release notes is their fault.

Best regards,
Daniel Vérité
PostgreSQL-powered mailer:
Twitter: @DanielVerite

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