Add important tricky todo

Author: lanlou1554

optd-cost-model/src/cost/filter/comp_op.rs

@@ -179,8 +179,8 @@ impl<S: CostModelStorageManager> CostModelImpl<S> {
                         cast_node = attr_ref_expr.into_pred_node();
                         // The "invert" cast is to invert the cast so that we're casting the
                         // non_cast_node to the attribute's original type.
-                        // TODO(migration): double check
                         // TODO: Consider attribute info is None.
+                        // **TODO**: What if this attribute is a derived attribute?
                         let attribute_info = self
                             .storage_manager
                             .get_attribute_info(table_id, attr_ref_idx as i32)

optd-cost-model/src/storage/persistent.rs

@@ -30,6 +30,8 @@ impl<S: CostModelStorageLayer + Send + Sync> CostModelStorageManager
     ///
     /// TODO: if we have memory cache,
     /// we should add the reference. (&Attr)
+    /// TODO(IMPORTANT): what if table is a derived (temporary) table? And what if
+    /// the attribute is a derived attribute?
     async fn get_attribute_info(
         &self,
         table_id: TableId,
@@ -58,6 +60,9 @@ impl<S: CostModelStorageLayer + Send + Sync> CostModelStorageManager
     ///
     /// TODO: Shall we pass in an epoch here to make sure that the statistics are from the same
     /// epoch?
+    ///
+    /// TODO(IMPORTANT): what if table is a derived (temporary) table? And what if
+    /// the attribute is a derived attribute?
     async fn get_attributes_comb_statistics(
         &self,
         table_id: TableId,