On Wed, Dec 23, 2015 at 09:45:14AM +0200, Achilleas Mantzios wrote:
Hello List,
We just finished a test upgrade using pg_upgrade from 9.0 to 9.3,
and the experience has been unexpectedly good! The database is just
Great.
a tad smaller than 1TB, and the upgrade last only seconds, using the
--link option.
Yep, the speed is quite unexpected.
I noticed that :
- Database specific options were correctly retained (e.g. bytea_output)
Yes, that is part of pg_dump.
- Next XID was correctly transferred to the new cluster
Yes, that is always done by pg_upgrade.
I'd like to ask, if we can rely on the above assumptions during the actual migration on the production system.
Yes.
Another consideration is --check. I didn't run it on the test
system. Is it a requirement? A plus? The doc says about using it in
--check is only a way to get early warnings about possible failures.
The checks are also run during an upgrade.
conjunction with --link to do enable link-mode-specific checks. What
does this do? From what I understand, running --check against the
It makes sure the old and new cluster are on the same file system, which
is a requirement for hard links.
existing running older system enables doing some checks and allowing
us to perform some preparation work in parallel before the actual
final pg_upgrade invocation. Is this true? Can anyone shed some
light on this?
Well, --check really just reports causes of failure before the actual
upgrade.
Another question is about --retain (I didn't use it either in our
test). I understand that it might transfer or make the links to the
old pg_log directory. The doc says "retain SQL and *log* files
*even* after a successful completion". What's the logic behind it?
Uh, it is really just for debugging in case there is a suspicion that
pg_upgrade is not working properly.
Why a special note on successful completion? If SQL logs are the
regular pg_log files, then which are the other *log* files the doc
mentions? Apparently it cannot be WAL (pg_xlog), since this is a
It is the SQL pg_dump files that were used by pg_upgrade, and the
postmaster server output log files generated during the upgrade. Again,
only useful for debugging of pg_upgrade.
different format than the old version, and would be of no use in the
new data cluster, just like the older PITR archived WALs. So, what's
the best practice regarding regular postgresql log file and
pg_uprage? How about pg_xlog? Should we just scrap the old ones,
move the new ones to the correct locations and re regenerate the
symlinks ? Sounds fair, I think.
pg_xlog files are not portable between major versions of Postgres and
should never be transfered. You just delete the old cluster when you
are done and the old pg_xlog files are removed as part of it.
