Row-level security in BigQuery is a feature that allows you to control access to rows in a table based on the user's identity or membership in a certain group. This ensures that users can only access the data they are permitted to see, enhancing the security of your data within BigQuery.

With the new feature in preview, you can use lookup tables in conjunction with the SESSION_USER function to filter the values that a principal should see. This allows for dynamic row-level access control based on user identity without the need to manually specify the access values.

The SESSION_USER function in BigQuery is used to retrieve the email address of the user who is running the query. This function can be utilized within row-level security policies to dynamically filter data access based on the user's identity.