On 08/12/2013 02:22 PM, Magnus Hagander wrote:
On Mon, Aug 12, 2013 at 8:14 PM, Andrew Dunstan <and...@dunslane.net> wrote:
On 08/12/2013 01:40 PM, Magnus Hagander wrote:
I also like the concept of #2, but I think we need to think about it a
bit more. One of the things I like about barman backups is that on
recovery you can map where tablespaces go, on a per tablespace basis
(it's not very well documented, or wasn't when I last looked, but it
does work). I think something like that would be awesome to have for
pg_basebackup. So allowing multiple options of the form
--map-tablespace c:/foo/bar=d:/baz/blurfl
or some such would be great.
Good point. I see now that the syntax I floated covered just one slice
of a
whole range of things folks might want in that area.
I think I have an old patch around for doing just the map-tablespace
thing that I never quite finished. That one was mostly useful for
setting up replicas really, since that's when you know at backup time
where you want to the new tablespaces to go. For a regular backup, you
want it to happen at restore time. And in this case, you're quite
likely working off the tarfiles, and we don't really have a program
dealing with the restore of those at all - you're just supposed to do
it manually.
A trivial tool that worked off the directory of tarfiles and allowed
remapping of the tablespace locations (by updating the
symlinks/junctions restored out of the base.tar flie) might be an
easier and less invasive way to do it than to put it in the actual
recovery code?
What barman does is to dissolve the symlink when making its backup (i.e
pg_tblspc/12345 becomes a directory in the backup instead of a symlink), and
store the info relating to the source symlink in its metadata file. On
restore it recreates the symlink. It's at that stage that you can modify its
default behaviour by specifying where the link should go.
Something like that makes sense for a plain format dump - but maybe
not for a tar one. And in either case, that also requires there to be
a pg_baserestore (or whatever you'd want to call it, please come up
with a better name :D) to do the restore process, to make sure it's
properly mapped.
I'm not saying to do it exactly as barman does. I'm just describing how
they do it.
I'd be quite happy if we just provided, at least to begin with,
tablespace mapping for plain format pg_basebackup dumps.
cheers
andrew
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