Partial implementation of Dismax component

No support yet for boost queries or boost functions

Author: Mat Brown

lib/soolr.rb

@@ -10,6 +10,8 @@ module Soolr
 
   autoload :Field, 'soolr/field'
 
+  autoload :Dismax, 'soolr/dismax'
+
   autoload :AllOf, 'soolr/all_of'
   autoload :AnyOf, 'soolr/any_of'
   autoload :Between, 'soolr/between'

lib/soolr/dismax.rb

@@ -0,0 +1,43 @@
+module Soolr
+  class Dismax
+    FieldWithBoost = Struct.new(:field, :boost, :phrase_boost)
+
+    attr_writer :minimum_match, :phrase_slop, :query_phrase_slop, :tie_breaker
+
+    def initialize(keywords)
+      @keywords, @fields = keywords, []
+    end
+
+    def add_field(field, options = {})
+      @fields << FieldWithBoost.new(field, options[:boost], options[:phrase_boost])
+    end
+
+    def to_params
+      fields = []
+      phrase_fields = []
+      @fields.each do |field_with_boost|
+        fields <<
+          if field_with_boost.boost
+            "#{field_with_boost.field.name}^#{field_with_boost.boost}"
+          else
+            field_with_boost.field.name
+          end
+        if field_with_boost.phrase_boost
+          phrase_fields << "#{field_with_boost.field.name}^#{field_with_boost.phrase_boost}"
+        end
+      end
+
+      params = {
+        :q => @keywords,
+        :qt => 'dismax',
+        :qf => fields.join(' ')
+      }
+      params[:mm] = @minimum_match if @minimum_match
+      params[:pf] = phrase_fields.join(' ') unless phrase_fields.empty?
+      params[:ps] = @phrase_slop if @phrase_slop
+      params[:qs] = @query_phrase_slop if @query_phrase_slop
+      params[:tie] = @tie_breaker if @tie_breaker
+      params
+    end
+  end
+end

spec/examples/dismax_spec.rb

@@ -0,0 +1,79 @@
+require File.expand_path('../spec_helper', __FILE__)
+
+describe Soolr::Dismax do
+  let(:headline) { Soolr::Field.new(:headline, Soolr::StringType) }
+  let(:body) { Soolr::Field.new(:body, Soolr::StringType) }
+
+  describe '#to_params' do
+    it 'should have :q param' do
+      params_from('pizza')[:q].should == 'pizza'
+    end
+
+    it 'should set :qt param to "dismax"' do
+      params_from('pizza')[:qt].should == 'dismax'
+    end
+
+    it 'should set :qf param' do
+      params_from('pizza') do |dismax|
+        dismax.add_field(headline)
+      end[:qf].should == 'headline'
+    end
+
+    it 'should set multiple fields in :qf param' do
+      params_from('pizza') do |dismax|
+        dismax.add_field(headline)
+        dismax.add_field(body)
+      end[:qf].should == 'headline body'
+    end
+
+    it 'should set boost in :qf param if given' do
+      params_from('pizza') do |dismax|
+        dismax.add_field(headline, :boost => 2.0)
+        dismax.add_field(body)
+      end[:qf].should == 'headline^2.0 body'
+    end
+
+    it 'should set minimum match' do
+      params_from('pizza pasta pepperoni') do |dismax|
+        dismax.minimum_match = 2
+      end[:mm].should == 2
+    end
+
+    it 'should set phrase fields' do
+      params_from('pizza') do |dismax|
+        dismax.add_field(headline, :phrase_boost => 5.0)
+        dismax.add_field(body, :phrase_boost => 2.0)
+      end[:pf].should == 'headline^5.0 body^2.0'
+    end
+
+    it 'should set phrase slop' do
+      params_from('pizza') do |dismax|
+        dismax.phrase_slop = 2
+      end[:ps].should == 2
+    end
+
+    it 'should set query phrase slop' do
+      params_from('pizza') do |dismax|
+        dismax.query_phrase_slop = 2
+      end[:qs].should == 2
+    end
+
+    it 'should set tie breaker' do
+      params_from('pizza') do |dismax|
+        dismax.tie_breaker = 0.1
+      end[:tie].should == 0.1
+    end
+  end
+
+  private
+
+  def dismax(keywords)
+    dismax = Soolr::Dismax.new(keywords)
+    yield dismax if block_given?
+    dismax
+  end
+
+  def params_from(keywords, &block)
+    dismax(keywords, &block).to_params
+  end
+end