Re: (A) native Windows port - Mailing list pgsql-hackers

On Wednesday 03 July 2002 12:09 pm, Bruce Momjian wrote:
> Hannu Krosing wrote:
> > AFAIK I can run as many backends as I like (up to some practical limit)
> > on the same comuter at the same time, as long as they use different
> > ports and different data directories.

> We don't have an automated system for doing this.  Certainly it is done
> all the time.

Good.  Dialog.  This is better than what I am used to when I bring up 
upgrading. :-)

Bruce, pg_upgrade isn't as kludgey as what I have been doing with the RPMset 
for these nearly three years.

No, what I envisioned was a standalone dumper that can produce dump output 
without having a backend at all.  If this dumper knows about the various 
binary formats, and knows how to get my data into a form I can then restore 
reliably, I will be satisfied.  If it can be easily automated so much the 
better.  Doing it table by table would be ok as well.

I'm looking for a sequence such as:

----
PGDATA=location/of/data/base
TEMPDATA=location/of/temp/space/on/same/file/system

mv $PGDATA/* $TEMPDATA
initdb -D $PGDATA
pg_dbdump $TEMPDATA |pg_restore  {with its associated options, etc}

With an rm -rf of $TEMPDATA much further down the pike.....

Keys to this working:
1.)    Must not require the old version executable backend.  There are a number 
of reasons why this might be, but the biggest is due to the way much 
upgrading works in practice -- the old executables are typically gone by the 
time the new package is installed.

2.)    Uses pg_dbdump of the new version.  This dumper can be tailored to provide 
the input pg_restore wants to see.  The dump-restore sequence has always had 
dumped-data version mismatch as its biggest problem -- there have been issues 
before where you would have to install the new version of pg_dump to run 
against the old backend.  This is unacceptable in the real world of binary 
packages.

One other usability note: why can't postmaster perform the steps of an initdb 
if -D points to an empty directory?  It's not that much code, is it?  (I know 
that one extra step isn't backbreaking, but I'm looking at this from a rank 
newbie's point of view -- or at least I'm trying to look at it in that way, 
as it's been a while since I was a rank newbie at PostgreSQL)  Oh well, just 
a random thought.

But I believe a backend-independent data dumper would be very useful in many 
contexts, particularly those where a backend cannot be run for whatever 
reason, but you need your data (corrupted system catalogs, high system load, 
whatever).  Upgrading is just one of those contexts.
-- 
Lamar Owen
WGCR Internet Radio
1 Peter 4:11