Once a new attribute is added, the data has to be re-indexed (reloaded). For the same, you will have to go to the dataset listings page and click on the ‘Clear’ link, located under the 'Select Action' drop down in front of the said dataset. This will clear the data present in the dataset. Now click on the ‘Check Status’ link. With this, you will navigate to the Loader page. Click on the ‘To start loading new data click here’ link on the loader page to start new data load. Now data will also be fetched in the newly added attribute column.