Chris Webb builds a relationship:
Many Power BI connectors for relational databases, such as the SQL Server connector, have an advanced option to control whether relationship columns are returned or not. By default this option is on. Returning these relationship columns adds a small overhead to the time taken to open a connection to a data source and so, for Power BI DirectQuery semantic models, turning this option off can improve report performance slightly.
Read on to learn what these relationship columns are and how you can remove them. Chris also provides a first-order approach to how you can estimate the performance pain involved with including these.