add some comments

core/translate/emitter.rs

@@ -1067,6 +1067,9 @@ fn emit_update_insns(
             });
         }
 
+        // If we are updating the rowid, we cannot rely on overwrite on the
+        // Insert instruction to update the cell. We need to first delete the current cell
+        // and later insert the updated record
         if has_user_provided_rowid {
             program.emit_insn(Insn::Delete { cursor_id });
         }

core/translate/update.rs

@@ -293,6 +293,7 @@ pub fn prepare_update_plan(
             .joined_tables()
             .first()
             .unwrap();
+        // We do not need to emit an ephemeral plan if we are not going to loop over the table values
         if matches!(table.op, Operation::Search(Search::RowidEq { .. })) {
             (None, vec![])
         } else {