Merge pull request sunspot#314 from throwern/master

order_by_function field query

README.md

@@ -443,6 +443,40 @@ Post.search do
 end
 ```
 
+**Solr 3.1 and above**
+
+Solr supports sorting on multiple fields using custom functions. Supported
+operators and more details are available on the [Solr Wiki](http://wiki.apache.org/solr/FunctionQuery) 
+
+To sort results by a custom function use the `order_by_function` method.
+Functions are defined with prefix notation:
+
+```ruby
+# Order by sum of two example fields: rating1 + rating2
+Post.search do
+  fulltext("pizza")
+  order_by_function(:sum, :rating1, :rating2, :desc)
+end
+
+# Order by nested functions: rating1 + (rating2*rating3)
+Post.search do
+  fulltext("pizza")
+  order_by_function(:sum, :rating1, [:product, :rating2, :rating3], :desc)
+end
+
+# Order by fields and constants: rating1 + (rating2 * 5)
+Post.search do
+  fulltext("pizza")
+  order_by_function(:sum, :rating1, [:product, :rating2, '5'], :desc)
+end
+
+# Order by average of three fields: (rating1 + rating2 + rating3) / 3
+Post.search do
+  fulltext("pizza")
+  order_by_function(:div, [:sum, :rating1, :rating2, :rating3], '3', :desc)
+end
+```
+
 ### Grouping
 
 **Solr 3.3 and above**

sunspot/lib/sunspot/dsl/field_query.rb

@@ -338,6 +338,30 @@ def dynamic(base_name, &block)
           &block
         )
       end
+      #
+      # Specify that results should be ordered based on a
+      # FunctionQuery - http://wiki.apache.org/solr/FunctionQuery
+      # Solr 3.1 and up
+      #
+      #  For example, to order by field1 + (field2*field3):
+      #
+      #    order_by_function :sum, :field1, [:product, :field2, :field3], :desc
+      #
+      # ==== Parameters
+      # function_name<Symbol>::
+      #   the function to run
+      # arguments::
+      #   the arguments for this function.
+      #   - Symbol for a field or function name
+      #   - Array for a nested function
+      #   - String for a literal constant
+      # direction<Symbol>::
+      #   :asc or :desc
+      def order_by_function(*args)
+        @query.add_sort(
+          Sunspot::Query::Sort::FunctionSort.new(@setup,args)
+        )
+      end
     end
   end
 end

sunspot/lib/sunspot/query/sort.rb

@@ -114,6 +114,41 @@ def to_param
           "geodist(#{@field.indexed_name.to_sym},#{@lat},#{@lon}) #{direction_for_solr}"
         end
       end
+
+      #
+      # A FunctionSort sorts by solr function.
+      # FunctionComp recursively parses arguments for nesting
+      #
+      class FunctionSort < Abstract
+        attr_reader :comp
+        def initialize(setup,args)
+          @direction = args.pop
+          @comp = FunctionComp.new(setup,args)
+        end
+        def to_param
+          "#{comp.to_s} #{direction_for_solr}"
+        end
+      end
+      class FunctionComp
+        attr_accessor :function,:fields
+        def initialize(setup,args)
+          @function=args.shift
+          @fields = []
+          args.each do |argument|
+            case argument.class.name
+            when "Array"
+              @fields<< FunctionComp.new(setup,argument)
+            when "Symbol"
+              @fields<< setup.field(argument).indexed_name
+            when "String"
+              @fields<< argument
+            end
+          end
+        end
+        def to_s
+          "#{function}(#{fields.map(&:to_s).join(",")})"
+        end
+      end
     end
   end
 end

sunspot/spec/integration/scoped_search_spec.rb

@@ -457,4 +457,24 @@ def self.test_field_type(name, attribute, field, *values)
       end
     end
   end
+
+  describe 'ordering by function' do
+    before :all do
+      Sunspot.remove_all
+      @p1 = Post.new(:blog_id => 1, :category_ids => [3])
+      @p2 = Post.new(:blog_id => 2, :category_ids => [1])
+      Sunspot.index([@p1,@p2])
+      Sunspot.commit
+    end
+    it 'should order by sum' do
+      # 1+3 > 2+1
+      search = Sunspot.search(Post) {order_by_function :sum, :blog_id, :primary_category_id, :desc}
+      search.results.first.should == @p1
+    end
+    it 'should order by product and sum' do
+      # 1 * (1+3) < 2 * (2+1)
+      search = Sunspot.search(Post) { order_by_function :product, :blog_id, [:sum,:blog_id,:primary_category_id], :desc}
+      search.results.first.should == @p2
+    end
+  end
 end