Row-level authorization in queries

Design authorization for a data-query platform where ABAC policies must filter ROWS, not just allow/deny a whole request: a query 'SELECT * FROM orders' should transparently return only the rows a user is allowed to see based on attributes (region, classification, ownership), across billions of rows, where calling a policy engine per row is impossible. The policies are admin-authored and change without redeploy. Discuss how you push authorization down into the query, the partial-evaluation idea that turns a policy into a predicate, how you handle policy changes mid-flight, and where caching is safe.