Whenever you load data from a QVD file, the load will be optimized. This means that loading the data will be from 10 to 100 times faster than any other source. However, if you make any operations within the load statement, Qlik Sense will have to uncompress the file to make those operations, losing speed.

There are two things that you can do within the load statement and still have an optimized and fast load:

• Rename the fields using the AS operator.
• Using the Exists() function in a Where clause. This function checks whether a specific field value has already been loaded in the script.