The APIs for moving a page currently conflate these three activities, I suspect because that's the way it's done in the user interface:

• Moving a page to a new space
• Moving a page to a new parent
• Moving a page to a different order within the same parent

This makes the APIs (and implementations) really complicated and is the source of a bunch of bugs. It would be much better if the API treated these things as three separate operations that could then be composed.

Some care would have to be taken: for example if you move a page to a new space then change its parent, you shouldn't have to rebuild the ancestor table more than once. Still, that's eminently doable.