The search code in the new codebase behaves similar to our current code in that it assumes an implicit AND for several search terms, and doesn't return any results if no articles match all terms.
I wonder if this is the intuitive behavior for most users. I think Google has conditioned people to type in as much relevant information as possible to get better hits, and most search engines work that way. In fact, the built-in mysql search code works that way too. Maybe we should use it directly? That way, we could also present the results according to relevancy (which mysql reports), rather than alphabetically.
We would lose the boolean AND OR NOT operators, but newer versions of mysql have substitutes: you use "+term" if you definitely want the term in your results, and you use "-term" if you definitely don't want it. This is almost as powerful as boolean searching.
Alternatively, we could have an "advanced search" page where you could construct a boolean search, include/exclude specific namespaces etc. Now that I think about it, a way to optionally search talk: and wikipedia: would probably be desirable.
Axel