Speed up fulltext search via indexing

db/migrate.rb

 
 def migrate
   db = connect
-  db.create_table :threads do
+  db.create_table? :threads do
     primary_key :id
     String :title
     String :creator, index: true
     DateTime :created_at, index: true
   end
 
-  db.create_table :posts do
+  db.create_table? :posts do
     primary_key :id
     String :body
     String :creator, index: true
     Integer :remote_id, index: true, unique: true
     foreign_key :thread_id, :threads
     DateTime :created_at, index: true
+    column :tsv, 'tsvector'
   end
 
-  db.create_function(:update_last_post, <<-SQL, language: :plpgsql, returns: :trigger)
+  db.run('CREATE INDEX tsv_idx ON posts USING gin(tsv);')
+
+  db.create_function?(:update_last_post, <<-SQL, language: :plpgsql, returns: :trigger)
     BEGIN
       UPDATE threads
       SET
     END
   SQL
 
+  db.create_function?(:set_posts_tsv, <<-SQL, language: :plpgsql, returns: :trigger)
+    BEGIN
+      NEW.tsv = to_tsvector(new.body);
+      RETURN NEW;
+    END
+  SQL
+
   db.run(<<-SQL)
     CREATE TRIGGER update_last_post
     AFTER INSERT ON posts
     FOR EACH ROW
     EXECUTE PROCEDURE update_last_post();
   SQL
+
+  db.run(<<-SQL)
+    CREATE TRIGGER set_posts_tsv
+    BEFORE INSERT OR UPDATE ON posts
+    FOR EACH ROW
+    EXECUTE PROCEDURE set_posts_tsv();
+  SQL
 end