by Jens Kramer

Ferret Library

http://ferret.davebalmain.com

. gem install ferret

the problem?
collected information, and suddenly someone needs to search it!

Ferret structure:
index
documents
fields

Indexing
index = Ferret::Index.new :path => ‘/tmp/index’

book.each do | book|
index < < {
:content => book.content,
:title => book.title,
:author => book.author
}
end

index.optimize
index.close

Searching

index.search_each(‘ruby’) do |doc_id, score|
doc = index[doc_id]
puts …
end
index.close

note: doc_id changes whenever you change your index, so not a good using it

Query Language
text based, very expressive, very powerful meta language basic queries
- fox
- w?ldcar*
- quick~0.5
- [20050725 20050905]
- “quick|speedy|fast <> fox”
- “quick|fast fox”~2
combined queries
- (quick fast) and fox
- +(qui* fast) -brown +fox
- description:(quick fast) and name:fox
- content:rails title:rails^5 +date: >= 20070101

Ferret Query API
sp_term_q = SpanTermQuery.new(:content, ‘rails’)
sp_first_q ) SpanFirstQuery.new(sp_term_q, 100)

result = index.search(sp_first_q)

Sorting
result = index.search(‘ruby’, :sort => ‘date DESC, title’)

sort = Ferret::Search::Sort.new(
Ferret::Search::SortField(:date, :reverse = true, type => :byte)
)

Ferret Browser
- interesting tool… :)
- comes with the gem
- lets you browse your index

Basic Usage in Rails

class Book < ActiveRecord::Base
acts_as_ferret
end

Book.rebuild.index
results = Book.find_with_ferret ...

Field Options
acts_as_ferret(
:fields => {
:title => {:store => :yes, :books => 10}
…
}
:ferret = {
:analyser => GermanSteammingAnalyser.new # custom analyser
}
)

Custom fields
that won’t go into the DB.
acts_as_ferret(
:fields => {
:title => {:store => :yes, :books => 10}
:booktitle => {} # custom!
}

? carefull this fields might be lost when you rebuild index

ActiveRecord Options
allow to modify default active record options

Lazy Options
store only partials not entire results

Multi_Search
you have multiple models, but you’ll need a single search method for an entire app
the only requirement, STORE THE CLASSNAME on the index:
acts_as_ferret(:fields = {…}, :store_classname => true)

(EXAMPLE)

Ferret out there in the wild:
omdb.org
xing.com
blogblogs.com.br
lingr.com
altlaw.org
pertior.com
sachsen-gesetze.de

Further Reading

Ferret Shorcut
Lucene in Action

ferret-talk@rubyforge.org
ferret.davebalmain.com
projects.jkraemer.net/act_as_ferret