add CAST AS TEXT; change how default_field is assigned

lib/text_to_sql_query.rb

@@ -29,7 +29,7 @@ class TextToSqlQuery
     case first_key
     when :DEFAULT_COLUMN
       escaped_node_value = handle_special_chars node_value
-      ["#{@default_field.to_s} ILIKE ?", "%#{escaped_node_value}%"]
+      ["CAST(#{@default_field.to_s} AS TEXT) ILIKE ?", "%#{escaped_node_value}%"]
     when :OPERATOR_OR
       generate_expression_for_logical_operator(:OR, node_value)
     when :OPERATOR_AND
@@ -53,7 +53,7 @@ class TextToSqlQuery
       if mapping.nil?
         raise "Unknown field '#{first_key.to_s}'"
       else
-        ["#{mapping.to_s} ILIKE ?", "%#{escaped_node_value}%"]
+        ["CAST(#{mapping.to_s} AS TEXT) ILIKE ?", "%#{escaped_node_value}%"]
       end
     end
   end