That's an interesting scenario Mike.

Previously, I only handled boolean-like terms, as the scenarios we were asked to support involved just those types of terms. Obviously, when the approach allows for more, more scenarios pop to mind :).

I think we may still be able to resolve that case, but it becomes much more complicated. My design approach of adding the +/- affected the entire posting element, whereas the scenario you describe affects the positions of the posting element. This calls for a more complicated design and solution.

My take on it is that if someone wants to update the catch-all field, then reindexing the document may not be such a bad idea anyway. The purpose of those incremental updates is to cope w/ high frequency of updates, which usually happen on metadata fields, and not title.

But since one could add the 'tags' to the catch-all field as well, it brings us to the same point - how do I remove the positions of term X that relate to the tag X and not the potentially original term X that existed in the document?

This is a very advanced case (and interesting). I don't want to hold up the discussion on it, but want to make sure we do not deviate from getting the more simpler cases in first. Depending on the API, this might be very easy to solve, but might also complicate matters. Maybe, for a incr-field-updates-v1, we can do without it?