Soundex searches allow for irregular spellings, particularly in English. Rather than use words as they are spelled, the search converts each word to a canonical spelling based on pronunciation. It then compares converted text to converted search terms. About indexer indexer uses a database of word occurrences. As an option, the search can rank matched documents based on the prevalence of the search words as compared to document length.
Boolean capability is straightforward, and it is planned.
In fact, the current functionality essentially defaults to an AND between every search word. Regular expressions would be nearly impossible to add to indexer , and I know of no database search system that prepares a list of which files contain text matching which regular expressions. Phrase and proximity searches are not currently performed, but they would not be difficult to implement. Basically, along with the number of occurrences of each word in each file, we would have to collect, for each file, a list of offsets where the word occurs. From this, we could deduce phrases and proximity.