Le 28/06/2012 11:37, Lee Hachadoorian a écrit :
On Thu, Jun 28, 2012 at 10:38 AM, Mathieu Basille
<basi...@ase-research.org> wrote:
Le 28/06/2012 10:32, Sandro Santilli a écrit :
On Thu, Jun 28, 2012 at 10:23:14AM -0400, Mathieu Basille wrote:
Dear list,
I need to proceed with a sensitive (and unfortunate) migration of
the computer which currently runs PostGIS from Debian to Windows. I
You'll need to invoke pg_dump using the -Fc (custom format) switch,
which gives you not an SQL but an indexed dump, needed for skipping
the parts you won't want to restore. postgis_restore.pl will take
care of the restore (and skipping).
Dear Sandro,
Thanks for the additional information. I didn't understand the specifics of
the -Fc switch (maybe something to add in the doc?). It seems I don't have
to worry too much with the PostgreSQL/PostGIS upgrade.
Manthieu,
-Fc specifies "custom format", which is basically Postgres' own dump
format. It is smaller and faster to dump/restore than plain text. It
also allows you at restore to selectively choose which tables or
schemas you want to restore. But it can only restore to a Postgres
database. Plain text, which builds the restore as SQL CREATE and
INSERT statements, is slower, but can often be restored to non-
Postgres databases. See
http://www.postgresql.org/docs/8.4/static/app-pgdump.html.
I see, thx for the explanation! For a PostGIS DB, I understand why this is
the preferred format (there's not real advantage of restoring a PostGIS DB
in a non-PostgreSQL DB...). I expected the PostGIS doc to mention it, but
should have indeed looked at the PostgreSQL doc first!
And yes, I'd do the upgrade on Unix first.
Once you go to windows you'll be alone in the dark ...
This is actually my main concern... I'm very familiar and happy with Debian,
and not at all with Windows... Anyway, the migration is not my call! I will
thus proceed with the upgrade first on Debian, and later switch to Windows.
pg_dump is designed to restore between different Postgres platforms
and from lower to higher versions. I have not done a Linux→Windows
migration, but I have done a Windows→Linux migration, and there were
no problems or incompatibilities in switching OSes. I don't see the
point of restoring to a machine you are going to wipe anyway, and
since the database structure and content won't have changed (even
though the version has), I believe you will end up with exactly the
same dump file.
Dear Lee,
I wonder whether the postgis_restore script would not alter the DB,
especially since I still use an old PostGIS version where raster_columns
was not yet a view... This is why it made sense to me to dump the whole DB
again at the end of the process (to have a clean DB). But I might be wrong
here.
The main reason about starting the upgrade with Debian first is that I
perfectly know how to restore the system (PostgreSQL/PostGIS + DB) in its
current state with Debian. Which means that I can break it all, I will be
able to come up with a functional system anyway (from a backup of the /main
directory). I understand your point of view about switching OSes though.
Still, I'm so much more familiar with Debian vs. Windows that I would
rather lose some time in the upgrade process than running critical
operations with Windows (i.e. upgrading PostGIS).
If you wanted to be paranoid about it, rather than restoring to the
machine you will wipe, maybe you have some other old piece of
equipment running Debian (or that you can install Debian on) that you
can restore to temporarily. Obviously, you wouldn't want to have
thousands of users hitting it, but Postgres/PostGIS runs quite well on
desktop-class hardware. This would also preserve access to your data
while you are setting up Windows, in case something goes wrong or it
takes longer than you expect.
This is actually a good idea! I'm currently running Debian on my own
laptop, which could serve as a basis for this upgrade (dump from the
server, upgrade on my computer). I'll need to check memory requirements
though (I might be short of space on my hard drive).
I'll let you know how all of this work!
Thanks again,
Mathieu.
--Lee
--
~$ whoami
Mathieu Basille, Post-Doc
~$ locate
Laboratoire d'Écologie Comportementale et de Conservation de la Faune
+ Centre d'Étude de la Forêt
Département de Biologie
Université Laval, Québec
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http://ase-research.org/basille
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``If you can't win by reason, go for volume.''
Calvin, by Bill Watterson.
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