"Massive data changes" in a single transaction aren't really a problem.
In my experience a single transaction changing a lot of rows is more
efficient than multiple transactions changing fewer rows.
That might work on a idle system but I would have to disagree with that statement. In theory it may be more efficient but it practice large long running transactions cause replication lag issues as well as vacuuming issues by holding on to older xmin value. Basically, they are bad for high transaction systems.