In response to Grzegorz Jaśkiewicz <gryzman@xxxxxxxxx>: > On Wed, Jun 3, 2009 at 8:14 PM, Bill Moran <wmoran@xxxxxxxxxxxxxxxxx> wrote: > > In response to "Carlos Oliva" <carlos@xxxxxxxxxxx>: > > > >> Woudl it be possible to keep the current postgresql version running in a > >> different port, install a new version of postgresql, and copy the data from > >> one version to the other while both versions are running? This might give > >> us time to copy the tables and databases one at a time and reconfigure the > >> database access for parts of the application until we complete the migration > >> to the new version. > > > > Your best bet would be to install Slony-I. One of the main design goals > > for Slony is to allow interruption-free upgrades. > > I don't think it is "easy", but will do if you need to synchronize > data before switching. "easy" was not the point. I gathered from his comments that downtime is an issue, and I know (from experience) that Slony provides the ability to upgrade with almost no downtime, even with very large databases. His plan of migrating tables one at a time may work, but it's frighteningly error-prone. If he copies a table, how does he know the data hasn't changed during the copy? What if he doesn't quite get all the clients switched over all at once? How do you do a JOIN when one table is in one database and the other somewhere else? Once the DBs are in sync with Slony, a single command will switch to the new server. If it doesn't go well (because he has a client compatibility problem, for example -- casts anyone?) it's a simple process to switch back, all with a guarantee that his data will never be lost, out of sync or corrupted. And if his application requires small downtime windows, this is a process he will benefit from getting familiar with anyway. -- Bill Moran http://www.potentialtech.com http://people.collaborativefusion.com/~wmoran/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
