In the codex it is explained how to hook to
plugin_loaded and check the version of the currently installed plugin against what's registered in the options, then realise if you need to upgrade the plugin table.
Question is - what's the method to do it with a multisite plugin that has custom database tables for each network blog? If I hook into
plugin_loaded then a random user who happens to be the first that executes the code will need to take all the load of this potentially huge and long process.
Isn't there any manual way to do it? somehow via cron? other suggestions?