opensoul.org

I love ferret (the ruby port of Lucene, not the fuzzy little creatures, you sicko). But something I fight on every project is that ferret turns into a bear when you try to get it to do partial matches, like "ferr" matching "ferret" and "ferrari".

Ferret allows you to append an asterisk to your search query ("ferr*"), which works great, but we can’t expect our users to do that because damn Google ¹ has set the expectation that search just works; I don’t need to use any funky syntax to find my pogs, Harry Potter gossip or BRATZ ².

So, we can do this manually in code by appending an asterisk to anything users enter and problem solved, right? Not quite.

• It breaks if you’re using the StemFilter, which allows you to match variations of words ("happy" would match "happiness" and "happiest")
• It will only match partials on the last word that the user entered ("Ed Brad" won’t find "Edward Bradley")
• Apparently the asterisk tells ferret that there has to be more characters, because full matches no longer work ("ferret*" won’t match "ferret")

So, here’s my hack.

Book.find_by_contents "(#{term})^2 OR (#{term.split.map {|t| t + "*" }.join(' ')})"

This ugly little thing will match exactly what the user entered (making use of stemming and all the magic that comes from it) and give it a little boost in the ranking, or match any part of any of the words entered, giving me partial matches.

I acknowledge that this is an ugly hack at the moment, and will break miserably if the user is any kind of a wizard that knows how to do advanced searches, but it works for now. I have no idea what kind of consequences this will have as far as search performance and such. The goal is to wrap this into a filter.

Any one else have any cleaver ideas for doing partial matches?

1. Yes, Google, we love and hate you for raising the bar.
2. We’re talking normal users here, which excludes anyone that is reading this.

Update: This is not needed with recent versions of acts_as_ferret.

Here’s a little nugget to add to acts_as_ferret to make your searches paginate with will_paginate.

module ActsAsFerret
  module ClassMethods
    def paginate_search(query, options = {})
      page, per_page, total = wp_parse_options(options)
      pager = WillPaginate::Collection.new(page, per_page, total)
      options.merge!(:offset => pager.offset, :limit => per_page)
      result = find_by_contents(query, options)
      returning WillPaginate::Collection.new(page, per_page, result.total_hits) do |pager|
        pager.replace result
      end
    end
  end
end

Updated from Behrang’s comment based on changes to will_paginate.

There was a slight challenge in that will_paginate expects that you do one query to get the count, create a new collection object based on that count, and then perform the actual search. But acts_as_ferret does it all in one method call, so I have to create a temporary collection object to get the offset, then do the search and create the collection object. It’s a little messier than it needs to be, but it works.

Product.paginate_search params[:q], :page => params[:page]