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The most significant update in this release is that you can now alter the
scoring, thereby altering the ordering of search results. A great application of
this is that you can now change the weight of a document based on its age. In
this example we have 365 day half life, ie a year-old document has half the
weight of a new document and twice the weight of a 2-year-old document;
require 'ferret'
age_weight = lambda do |doc, score, searcher|
age = (Date.today - Date.parse(searcher[doc][:date])).to_i
1 / 2 ** (age.to_f/365)
end
index = Ferret::I.new
sales = [
{ :artist => 'Giovanni Bellini',
:date => '2006-10-23',
:work => 'Transfiguration'
},
{ :artist => 'Giovanni Bellini',
:date => '2008-01-05',
:work => 'Pesaro Altarpiece'
},
{ :artist => 'Gentile Bellini',
:date => '2008-02-10',
:work => 'St. Dominic'
},
].each {|doc| index << doc}
puts index.search('artist:(Giovanni Bellini)').to_s(:work)
# =>
# TopDocs: total_hits = 3, max_score = 0.767351 [
# 0 "Transfiguration": 0.767351
# 1 "Pesaro Altarpiece": 0.767351
# 2 "St. Dominic": 0.129147
# ]
puts index.search('artist:(Giovanni Bellini)',
:filter_proc => age_weight).to_s(:work)
# =>
# TopDocs: total_hits = 3, max_score = 0.718006 [
# 1 "Pesaro Altarpiece": 0.718006
# 0 "Transfiguration": 0.311937
# 2 "St. Dominic": 0.129147
# ]
You can also now write your own C extensions to filter the search results. You
can see an example of this by downloading the source and looking at;
ferret_unzipped/ruby/examples/c_extensions/age_filter/
Alternatively, you can view the code at;
http://ferret.davebalmain.com/trac/browser/trunk/ruby/examples/c_extensions?rev=828
Also, good news for Norwegians, Romanians, Turks and Finns. We now have 3 new
stemmers for Norwegian, Romanian and Turkish and 2 new stop-word lists for
Finnish and Hungarian. Please try them out and let me know if there are any
problems.
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