Add a comment about potentiall returning reference to id hash-set in fetch_ids_from_index.

minisql/src/internals/table.rs

@@ -218,6 +218,9 @@ impl Table {
         } else {
             match self.indexes.get(&column_position) {
                 Some(index) => {
+                    // Note that we are cloning the ids here! This can be very wasteful in some cases.
+                    // It would be possible to just return a reference,
+                    // but this seems fairly non-trivial.
                     let ids = index.get(value).cloned();
                     Ok(ids)
                 }