Fuzzily - fuzzy string matching for ActiveRecord

This version of fuzzily contains experimental extensions to the original gem. Unless you seriously want some of the extensions - further described below - please use the original gem.

Show me photos of Marakech !

Here aresome photos of Marrakesh, Morroco. Did you mean Martanesh, Albania, Marakkanam, India, or Marasheshty, Romania?

Fuzzily finds misspelled, prefix, or partial needles in a haystack of strings. It's a fast, trigram-based, database-backed fuzzy string search/match engine for Rails. Loosely inspired from an old blog post.

Tested with ActiveRecord (2.3, 3.0, 3.1, 3.2, 4.0) on various Rubies (1.8.7, 1.9.2, 1.9.3, 2.0.0) and the most common adapters (SQLite3, MySQL, and PostgreSQL).

If your dateset is big, if you need yet more speed, or do not use ActiveRecord, check out blurrily, another gem (backed with a C extension) with the same intent.

Installation

Add this line to your application's Gemfile:

gem 'fuzzily'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fuzzily

Usage

You'll need to setup 2 things:

• a trigram model (your search index) and its migration
• the model you want to search for

Create and ActiveRecord model in your app (this will be used to store a "fuzzy index" of all the models and fields you will be indexing):

class Trigram < ActiveRecord::Base
  include Fuzzily::Model
end

Create a migration for it:

class AddTrigramsModel < ActiveRecord::Migration
  extend Fuzzily::Migration
end

Instrument your model:

class MyStuff < ActiveRecord::Base
  # assuming my_stuffs has a 'name' attribute
  fuzzily_searchable :name
end

Index your model (will happen automatically for new/updated records):

MyStuff.bulk_update_fuzzy_name

Search!

MyStuff.find_by_fuzzy_name('Some Name', :limit => 10)
# => records

You can force an update on a specific record with

MyStuff.find(123).update_fuzzy_name!

Indexing more than one field

Just list all the field you want to index, or call fuzzily_searchable more than once:

class MyStuff < ActiveRecord::Base
  fuzzily_searchable :name_fr, :name_en
  fuzzily_searchable :name_de
end

Custom name for the index model

If you want or need to name your index model differently (e.g. because you already have a class called Trigram):

class CustomTrigram < ActiveRecord::Base
  include Fuzzily::Model
end

class AddTrigramsModel < ActiveRecord::Migration
  extend Fuzzily::Migration
  self.trigrams_table_name = :custom_trigrams
end

class MyStuff < ActiveRecord::Base
  fuzzily_searchable :name, :class_name => 'CustomTrigram'
end

Speeding things up

For large data sets (millions of rows to index), the "compatible" storage used by default will typically no longer be enough to keep the index small enough.

Users have reported major improvements (2 order of magnitude) when turning the owner_type and fuzzy_field columns of the trigrams table from VARCHAR (the default) into ENUM. This is particularly efficient with MySQL and pgSQL.

This is not the default in the gem as ActiveRecord does not suport ENUM columns in any version.

UUID's

When using Rails 4 with UUID's, you will need to change the owner_id column type to UUID.

class AddTrigramsModel < ActiveRecord::Migration
  extend Fuzzily::Migration
  trigrams_owner_id_column_type = :uuid
end

Model primary key (id) is VARCHAR

If you set your Model primary key (id) AS VARCHAR instead of INT, you will need to change the owner_id column type from INT to VARCHAR in the trigrams table.

Searching virtual attributes

Your searchable fields do not have to be stored, they can be dynamic methods too. Just remember to add a virtual change method as well. For instance, if you model has first_name and last_name attributes, and you want to index a compound name dynamic attribute:

class Employee < ActiveRecord::Base
  fuzzily_searchable :name
  def name
    "#{first_name} #{last_name}"
  end

  def name_changed?
    first_name_changed? || last_name_changed?
  end
end

Limit the returned matches using the Jaro-Winkler distance

The basic trigram fuzzy search returns a list of the best trigram matches. You can set the number of returned matches using the :limit parameter (defaults to 10). However it may very well be the case that some of the returned results, say number 9 and 10, have very little ressemblance with the search pattern. We therefore add a set of distance filters that allow you to filter out any item whose ressemblance with the pattern falls below a given threshold. For this we rely on the Jaro-Winkler distance, as implemented by the fuzzy-string-match gem.

In order to allow best flexibility, the Jaro-Winkler distance threshold may be measured against one or several attributes of the model, which do not have to be the same attribute as the one used for the trigram matching. A useful example to explain this is when your (person/user) model has attributes 'firstname' and 'lastname' and you also have a virtual attribute 'name' which is the concatenation of the other two. In your person/user model you could do:

fuzzily_searchable :name

then to perform a search you could do:

Person.find\_by\_fuzzy\_name("John Smith",
          {:distance_filter =>[["lastname", "Smith", 0.6], ["firstname", "John", 0.5]]})

In this case, the results returned would exclude any person where the Jaro-Winkler measure is below 0.6 for the lastname or 0.5 for the firstname (The Jaro-Winkler measure is a floating point number between 0 and 1, where 0 means no match and 1 perfect match).

Extensions provided compared to the original gem

This version of fuzzily contains experimental extensions to the original gem. Unless you seriously want some of the extensions - further described below - please use the original gem.

• Branch mass_assignment: Avoid problems related to mass-assignment (this feature is now merged into the original gem)
• Branch apply_on_scope: same as mass_assignment + makes it possible to apply find_by_fuzzy on a relation/scope, like for example: Person.where('country = ?', "France").find_by_fuzzy_name(the_name, :limit => 20)
• Branch distance: same as apply_on_scope + limit the returned matches to those that satisfy aditing distance conditions, using the Jaro-Winkler distance algorithm.
• Branch limit_by_distance: boolean. If true, the limit option (which defaults to 10) is not used, only the distance conditions. Default: false
• Branch master: distance filter works also on virtual attributes

License

MIT licence. Quite permissive if you ask me.

Copyright (c) 2013 HouseTrip Ltd.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Thanks to @bclennox, @fdegiuli, @nickbender, @Shanison, @rickbutton for pointing out and/or helping on various issues.