Re: [HACKERS] PGXLOG variable worthwhile?

"Marc G. Fournier" <scrappy(at)hub(dot)org> writes:
> On Wed, 18 Sep 2002, Bruce Momjian wrote:
>> Sorry, I don't see the logic here. Using postgresql.conf, you set it
>> once and it remains set until you change it again. With -X, you have to
>> use it every time. I think that's where the votes came from.

> Ah, so you are saying that you type out your full command line each and
> every time you start up the server?

Let's put it this way: would you be in favor of adding a
--please-don't-wipe-my-database-directory
switch to the postmaster? And if you forget to specify that every time
you start the postmaster, we do an instant "rm -rf $PGDATA"?

Doesn't seem like a good idea, does it?

Well, specifying the XLOG location on the command line or as an
environment variable is just about as deadly as the above loaded-gun-
pointed-at-foot scenario. You start the postmaster with the wrong
context, even once, it's sayonara to your data integrity.

The point of insisting that the XLOG location be recorded *inside*
the data directory is to prevent simple admin errors from being
catastrophic. Do you remember when we regularly saw trouble reports
from people who'd corrupted their database indexes by starting the
postmaster with different LOCALE environments at different times? We
fixed that by forcing the locale collation order to be specified inside
the database directory (in pg_control, but the details are not important
here), rather than allowing it to be taken from postmaster environment.

If we allow XLOG location to be determined by a postmaster switch or
environment variable, then we *will* be opening the door for people
to shoot themselves in the foot just like they used to do with locale.

I learned something from those problems, and I do not intend to make
the same mistake again.

regards, tom lane