chore: Optimize Filter() for small lists (#4282)

coderd/rbac/authz.go

@@ -39,8 +39,26 @@ func Filter[O Objecter](ctx context.Context, auth Authorizer, subjID string, sub
 		return objects, nil
 	}
 	objectType := objects[0].RBACObject().Type
-
 	filtered := make([]O, 0)
+
+	// Running benchmarks on this function, it is **always** faster to call
+	// auth.ByRoleName on <10 objects. This is because the overhead of
+	// 'PrepareByRoleName'. Once we cross 10 objects, then it starts to become
+	// faster
+	if len(objects) < 10 {
+		for _, o := range objects {
+			rbacObj := o.RBACObject()
+			if rbacObj.Type != objectType {
+				return nil, xerrors.Errorf("object types must be uniform across the set (%s), found %s", objectType, rbacObj)
+			}
+			err := auth.ByRoleName(ctx, subjID, subjRoles, scope, action, o.RBACObject())
+			if err == nil {
+				filtered = append(filtered, o)
+			}
+		}
+		return filtered, nil
+	}
+
 	prepared, err := auth.PrepareByRoleName(ctx, subjID, subjRoles, scope, action, objectType)
 	if err != nil {
 		return nil, xerrors.Errorf("prepare: %w", err)