Avoid casting a tsvector column to text and back again.

lib/pg_search/configuration/column.rb

@@ -18,7 +18,16 @@ def full_name
       end
 
       def to_sql
-        "coalesce(#{expression}::text, '')"
+        coalesce("#{expression}::text")
+      end
+
+      def to_sql_no_cast
+        coalesce(expression)
+      end
+
+      def tsvector?
+        psql_column = @model.columns_hash[name]
+        psql_column && psql_column.type.eql?(:tsvector)
       end
 
       private
@@ -34,6 +43,10 @@ def column_name
       def expression
         full_name
       end
+
+      def coalesce(value)
+        "coalesce(#{value}, '')"
+      end
     end
   end
 end

lib/pg_search/features/tsearch.rb

@@ -122,16 +122,20 @@ def columns_to_use
       end
 
       def column_to_tsvector(search_column)
-        tsvector = Arel::Nodes::NamedFunction.new(
-          "to_tsvector",
-          [dictionary, Arel.sql(normalize(search_column.to_sql))]
-        ).to_sql
-
-        if search_column.weight.nil?
-          tsvector
+        if search_column.tsvector?
+          tsvector = Arel.sql(normalize(search_column.to_sql_no_cast))
         else
-          "setweight(#{tsvector}, #{connection.quote(search_column.weight)})"
+          tsvector = Arel::Nodes::NamedFunction.new(
+            "to_tsvector",
+            [dictionary, Arel.sql(normalize(search_column.to_sql))]
+          ).to_sql
         end
+
+        if search_column.weight
+          tsvector = "setweight(#{tsvector}, #{connection.quote(search_column.weight)})"
+        end
+
+        tsvector
       end
     end
   end