Just to add... When we load a plugin, we always look at any SQL parameters to see what tables are going to be modified by the plugin. We make a note of these in the website's "manual logbook" - hand-written (or printed out notes) that we archive. We use these notes for all maintenance, upgrade and plugin install activity. By knowing what tables are altered, we can get a better idea of the likelihood of potential conflicts that may arise, if php code tries to make calls to a table (field) that is either no longer there, or may have undergone some change or other.