postgresql based search performs poorly (natural language and structured)

Our search facilities, both natural language and structured, are performing poorly, giving an average-at-best user experience, and need to be overhauled.

There is a LEP : https://dev.launchpad.net/LEP/Search where the requirements gathering etc is taking place.

This bug is to permit referencing this effort in XXX comments in patches and code as per our regular XXX practice, and can be closed when we have a new search engine in place with code able to transition across to it.

I'm creating this as high as fixing search is a necessary condition to fixing numerous performance and usability issues, even though I know its not at the front of any teams queue today :- progressing it is near the front of my queue, and I'll be working on this.