Database Reference
In-Depth Information
How it works...
pg_upgrade
works easily because the data block format hasn't changed between some
releases. That won't always be the case; however, replication might not work across major
upgrades as well, though has done so for the last seven releases of PostgreSQL.
pg_upgrade
works by creating a new set of database catalog tables, and then creating the
old objects again in the new tables. This works well for common cases.
There's more...
If you're upgrading more than one major release, then we hope it should be possible. We do
this by allowing a chain of upgrade steps that takes you through the versions one-by-one. It
will be more complex to do things that way, though its the same general procedure.
Whatever you do, carefully plan the tests that will tell you whether the upgrade was successful
and whether it will be safe to continue.
Major upgrades online using replication
tools
Upgrading between major releases is hard, and should be deferred until you have some good
reasons and sufficient time to get it right.
You can use replication tools to minimize the downtime required for an upgrade, so we refer to
the following recipe as
online
upgrade
.
