Support a custom ts_rank function e.g. ts_rank_cd.

lib/pg_search/features/tsearch.rb

@@ -7,7 +7,7 @@ module PgSearch
   module Features
     class TSearch < Feature # rubocop:disable Metrics/ClassLength
       def self.valid_options
-        super + %i[dictionary prefix negation any_word normalization tsvector_column highlight]
+        super + %i[dictionary prefix negation any_word normalization tsvector_column ts_rank_function highlight]
       end
 
       def conditions
@@ -168,8 +168,12 @@ def normalization
         options[:normalization] || 0
       end
 
+      def ts_rank_function
+        options[:ts_rank_function] || "ts_rank"
+      end
+
       def tsearch_rank
-        Arel::Nodes::NamedFunction.new("ts_rank", [
+        Arel::Nodes::NamedFunction.new(ts_rank_function, [
           arel_wrap(tsdocument),
           arel_wrap(tsquery),
           normalization

spec/lib/pg_search/features/tsearch_spec.rb

@@ -27,6 +27,22 @@
         %{(ts_rank((to_tsvector('simple', coalesce(#{Model.quoted_table_name}."name"::text, '')) || to_tsvector('simple', coalesce(#{Model.quoted_table_name}."content"::text, ''))), (to_tsquery('simple', ''' ' || 'query' || ' ''')), 0))}
       )
     end
+
+    it "supports an expression using the ts_rank_cd() function" do
+      query = "query"
+      columns = [
+        PgSearch::Configuration::Column.new(:name, nil, Model),
+        PgSearch::Configuration::Column.new(:content, nil, Model)
+      ]
+      options = {ts_rank_function: 'ts_rank_cd'}
+      config = double(:config, :ignore => [])
+      normalizer = PgSearch::Normalizer.new(config)
+
+      feature = described_class.new(query, options, columns, Model, normalizer)
+      expect(feature.rank.to_sql).to eq(
+        %{(ts_rank_cd((to_tsvector('simple', coalesce(#{Model.quoted_table_name}."name"::text, '')) || to_tsvector('simple', coalesce(#{Model.quoted_table_name}."content"::text, ''))), (to_tsquery('simple', ''' ' || 'query' || ' ''')), 0))}
+      )
+    end
   end
 
   describe "#conditions" do