If you're working with a large codebase, then it might be time to look for a more powerful solution than conventional tools. OpenGrok is a very fast source code search and cross-reference engine. On top of its great performance, it integrates with Subversion, Mercurial, and ClearCase, among other source revision control software. It sounds a lot like something you could use.
If you want support to use OpenGrok from within Vim, you could easily write a vim function that would call system()
to start the search for you. To read more about writing new vim commands, look up :help 40.2
within vim.
I hope that's what you were looking for.
:Ack --ruby *something*
will generally return in a second or two, since it is searching only a subset of files – Titanesque