will this approach work?

i have a theoretical question... i need search functionality sort of
like Mac OSX spotlight. i was considering using ActsAsTaggable and
programmatically replacing the tags for a given object every time it is
saved. basically i would just dump all of the column values into tags.
i don't want dangling tags left in the tags table when objects are
changed or deleted. is this possible? what problems might i run into
with this?

Your main problem will be performance. On top of that, you’re duplicating a lot of data. If you want a performant model-wide search, you should look into a fulltext indexing engine like Ferret (Ruby version of Lucene) and the acts_as_ferret plugin. There are a few other fulltext search engines out there. Using such a plugin will also give you some extra features such as fuzzy searches (cfr. google’s “Did you mean…”) and inclusion/exclusion (cfr. google’s “+iwantthis -butnotthis”) and quite a lot of other very interesting extras.

Best regards

Peter De Berdt