Add tsvector_column option to pg_search_scope.

With this option, tsearch and dmetaphone searches can search against a
tsvector column to speed up search.

README.rdoc

@@ -302,6 +302,32 @@ Ignoring accents uses the {unaccent contrib package}[http://www.postgresql.org/d
   SpanishQuestion.gringo_search("Que") # => [what]
   SpanishQuestion.gringo_search("Cüåñtô") # => [how_many]
 
+=== Using tsvector columns
+
+PostgreSQL allows you the ability to search against a column with type tsvector instead of using an expression; this speeds up searching dramatically as it offloads creation of the tsvector that the tsquery is evaluated against.
+
+To use this functionality you'll need to do a few things:
+
+* Create a column of type tsvector that you'd like to search against. If you want to search using multiple search methods, for example tsearch and dmetaphone, you'll need a column for each.
+* Create a trigger function that will update the column(s) using the expression appropriate for that type of search. See: http://www.postgresql.org/docs/current/static/textsearch-features.html#TEXTSEARCH-UPDATE-TRIGGERS
+* Should you have any pre-existing data in the table, update the newly-created tsvector columns with the expression that your trigger function uses.
+* Add the option to pg_search_scope, e.g:
+
+  pg_search_scope :fast_content_search,
+                  :against => :content,
+                  :using => {
+                    dmetaphone: {
+                      tsvector_column: 'tsvector_content_dmetaphone'
+                    },
+                    tsearch: {
+                      dictionary: 'english',
+                      tsvector_column: 'tsvector_content_tsearch'
+                    }
+                    trigram: {} # trigram does not use tsvectors
+                  }
+
+Please note that the :against column is only used when the tsvector_column is not present for the search type.
+
 == REQUIREMENTS
 
 * ActiveRecord 2 or 3

lib/pg_search/features/tsearch.rb

@@ -50,10 +50,14 @@ def tsquery
       end
 
       def tsdocument
-        @columns.map do |search_column|
-          tsvector = "to_tsvector(:dictionary, #{@normalizer.add_normalization(search_column.to_sql)})"
-          search_column.weight.nil? ? tsvector : "setweight(#{tsvector}, #{connection.quote(search_column.weight)})"
-        end.join(" || ")
+        if @options[:tsvector_column]
+          @options[:tsvector_column].to_s
+        else
+          @columns.map do |search_column|
+            tsvector = "to_tsvector(:dictionary, #{@normalizer.add_normalization(search_column.to_sql)})"
+            search_column.weight.nil? ? tsvector : "setweight(#{tsvector}, #{connection.quote(search_column.weight)})"
+          end.join(" || ")
+        end
       end
 
       def tsearch_rank

spec/pg_search_spec.rb

@@ -523,6 +523,46 @@
       end
     end
 
+    context "using a tsvector column" do
+      with_model :ModelWithPgSearchUsingTsVectorColumn do
+        table do |t|
+          t.text 'content'
+          t.tsvector 'content_tsvector'
+        end
+
+        model { include PgSearch }
+      end
+
+      let!(:expected) { ModelWithPgSearchUsingTsVectorColumn.create!(:content => 'tiling is grouty') }
+      let!(:unexpected) { ModelWithPgSearchUsingTsVectorColumn.create!(:content => 'longcat is looooooooong') }
+
+      before do
+        ActiveRecord::Base.connection.execute <<-SQL
+          UPDATE #{ModelWithPgSearchUsingTsVectorColumn.table_name}
+          SET content_tsvector = to_tsvector('english'::regconfig, "#{ModelWithPgSearchUsingTsVectorColumn.table_name}"."content")
+        SQL
+
+        ModelWithPgSearchUsingTsVectorColumn.class_eval do
+          pg_search_scope :search_by_content_with_tsvector,
+            :against => :content,
+            :using => {
+              :tsearch => {
+                :tsvector_column => 'content_tsvector',
+                :dictionary => 'english'
+              }
+            }
+        end
+      end
+
+      it "should not use to_tsvector in the query" do
+        ModelWithPgSearchUsingTsVectorColumn.search_by_content_with_tsvector("tiles").to_sql.should_not =~ /to_tsvector/
+      end
+
+      it "should find the expected result" do
+        ModelWithPgSearchUsingTsVectorColumn.search_by_content_with_tsvector("tiles").map(&:id).should == [expected.id]
+      end
+    end
+
     context "ignoring accents" do
       before do
         model_with_pg_search.class_eval do