Should I re-install a database backup after performing a SPIP update?

No! Certainly not! Never ever! Non! Nichts! Niet!

Read what follows very carefully: "You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP. You should never install an old backup of the database over a new version of SPIP."

Go figure why, but one day someone announced on the SPIP mailing list that it should be done, and despite all our efforts to expose the contrary, there are still some users who are convinced that an old backup of the database should be re-installed when a new version of SPIP is installed.

It is a fatal error, worse than a virus in an Outlook mail client. Your computer will catch fire, your hard disk will melt, your host will be bankrupt, the Inland Revenue will clamp down on you and you’ll be barred from using the Internet for life.

The right procedure to perform an update is explained here