The upgrade of xwiki-tomcat9-common or xwiki-tomcat8-common can take ages when /var/lib/xwiki/data folder contains a lot of files

During configuration the Debian package do a

chown -R tomcat.tomcat /var/lib/xwiki/data

but chown can be very slow if there is a lot of file and it's actually completely useless most of the time, the only problem is when moving from one version of tomcat to another (and only if the use changes like between tomcat8 and tomcat9 packages but it might not be the case anymore since Tomcat9 now uses "tomcat" as user).