Full-text search using n-gram matching for the Mongoid ODM. Works for MongoDB 1.6, support for 1.8 coming soon.
Suppose you have an Artist model and want to index each artist's name:
class Artist
include Mongoid::Document
include Mongoid::FullTextSearch
field :first_name
field :last_name
def name
[first_name, last_name].join(' ')
end
fulltext_search_in :name
end
The fulltext_search_in directive will index the full name of the artist, so now
you can call:
Artist.fulltext_search("vince vangogh")
which will return an array of the Artist instances that best match the search string. Most likely, Vincent van Gogh will be included in the results. You can index multiple fields with the same index, so we can get the same effect of our Artist index above using:
class Artist
include Mongoid::Document
include Mongoid::FullTextSearch
field :first_name
field :last_name
fulltext_search_in :first_name, :last_name
end
To restrict the number of results returned, pass the :max_results parameter to fulltext_search:
Artist.fulltext_search("vince vangogh", :max_results => 5)
If you don't specify a field to index, the default is the result of to_s called on the object.
The following definition will index the first and last name of an artist:
class Artist
include Mongoid::Document
include Mongoid::FullTextSearch
field :first_name
field :last_name
def to_s
'%s %s' % [first_name, last_name]
end
fulltext_search_in
end
The full-text index is stored in a separate MongoDB collection in the same database as the
models you're indexing. By default, the name of this collection is generated for you. Above,
a collection named something like mongoid_fulltext.index_artist_0 will be created to
hold the index data. You can override this naming and provide your own collection name with
the :index_name parameter:
class Artwork
include Mongoid::Document
include Mongoid::FullTextSearch
field :title
fulltext_search_in :title, :index_name => 'mongoid_fulltext.foobar'
end
You can also create multiple indexes on a single model, in which case you'll want to provide index names:
class Artwork
include Mongoid::Document
include Mongoid::FullTextSearch
field :title
field :artist_name
field :gallery_name
filed :gallery_address
fulltext_search_in :title, :index_name => 'title_index'
fulltext_search_in :artist_name, :index_name => 'artist_name_index'
fulltext_search_in :gallery_name, :gallery_address, :index_name => 'gallery_index'
end
The index names are helpful now because you'll have to specify which one you want to use when you
call fulltext_search:
Artwork.fulltext_search('warhol', :index => 'artist_name_index')
If you have multiple indexes specified and you don't supply a name to fulltext_search, the
method call will raise an exception.
If you're indexing multiple models, you may find that you need to combine results to create
a single result set. For example, if both the Artist model and the Artwork model are
indexed for full-text search, then to get results from both, you'd have to call
Artist.fulltext_search and Artwork.fulltext_search and combine the results yourself. If
your intention is instead to get the top k results from both Artists and Artworks, you can
merge both into a single index by using the same :external_index parameter:
class Artwork
include Mongoid::Document
include Mongoid::FullTextSearch
field :title
fulltext_search_in :title, :index_name => 'artwork_and_artists'
end
class Artist
include Mongoid::Document
include Mongoid::FullTextSearch
field :name
fulltext_search_in :name, :index_name => 'artwork_and_artists'
end
Now that these two models share the same external index collection, we can search them both through
either model's fulltext_search method:
Artwork.fulltext_search('picasso') # returns same results as Artist.fulltext_search('picasso')
If you want to filter the results from full-text search, you set up filters when the indexes are
defined. For example, suppose that in addition to wanting to use the artwork_and_artists index
defined above to search for Artworks or Artists, we want to be able to run full-text searches
for artists only and for artworks priced above $10,000. Instead of creating two new indexes or
attempting to filter the results after the query is run, we can specify the filter predicates
at the time of index definition:
class Artwork
include Mongoid::Document
include Mongoid::FullTextSearch
field :title
field :price
fulltext_search_in :title, :index_name => 'artwork_and_artists',
:filters => { :is_expensive => lambda { |x| x.price > 10000 },
:has_long_name => lambda { |x| x.title.length > 20 }}
end
class Artist
include Mongoid::Document
include Mongoid::FullTextSearch
field :name
field :birth_year
fulltext_search_in :name, :index_name => 'artwork_and_artists',
:filters => { :born_before_1900 => lambda { |x| x.birth_year < 1900 },
:has_long_name => lambda { |x| x.name.length > 20}}
end
After defining filters, you can query for results that match particular values of filters:
# Only return artists born before 1900 that match 'foobar'
Artist.fulltext_search('foobar', :born_before_1900 => true)
# Return artists or artworks that match 'foobar' and have short names
Artist.fulltext_search('foobar', :has_long_name => false)
# Only return artworks with prices over 10000 that match 'mona lisa'
Artwork.fulltext_search('mona lisa', :is_expensive => true)
# Only return artworks with prices less than 10000 that match 'mona lisa'
Artwork.fulltext_search('mona lisa', :is_expensive => false)
Note that in all of the example queries above, supplying a filter that is defined on exactly
one of the models will restrict the search to results from that model only. For example,
since :is_expensive is defined only on Artworks, a call to fulltext_search with either
:is_expensive => true or :is_expensive => false will return only Artwork results.
You can specify multiple filters per index and per model. Each filter is a predicate that will
be called on objects as they're inserted into the full-text index (any time the model is saved.)
Filters are only called on instances
of models they're defined on, so in the example above, the is_expensive filter is only applied
to instances of Artwork and the born_before_1900 filter is only applied to instances of Artist,
although both filters can be used when querying from either model. The has_long_name filter, on
the other hand, will return instances of both Artwork and Artist since it's defined on each model
Filters shouldn't ever throw, but if they do, the filter is just ignored. If you apply filters to
indexes that are on multiple fields, the filter is applied to each field and the filter result is
the AND of all of the individual results for each of the fields. Finally, if a filter is defined
but criteria for that filter aren't passed to fulltext_search, the result is as if the filter
had never been defined - you see both models that both pass and fail the filter in the results.
To run the specs, execute rake spec. You need a local MongoDB instance to run the specs.