I was doing some work for a customer this week – they had a performance issue with a Power BI report. The data in the workbook wasn’t overly large, about 400,000 rows, yet the file size was 110 megabytes and the performance of the model was relatively slow given the number of records. When I looked at the report I noted that the report was using GUIDs between the primary and foreign keys on a number of tables. Generally speaking, it is not good practice to use a GUID to join tables, as GUIDs do not compress well and have a negative effect on the efficiency of physical 1 to many relationships.
Read on to learn more as well as what you can do about it.