This isn't an exact pattern searching library. Wade originally used Boyer-Moore, but has since switched to a trie [1] structure to search for _terms_ rather than the whole query.
This allows for result documents that can contain some of the terms, all of the terms, or a prefix of a term. It's also pretty fast as it doesn't need to run a linear search through the documents. I'm not sure what you mean by "classical" search algorithms, but a trie based search is a pretty standard way of doing it.