@Override
  protected void insertSubIndexEntry(int base, String key, String rec, SchemaPageContext cxt)
      throws MetadataException, IOException {
    insertAliasIndexEntry(getPageInstance(base, cxt), key, rec, cxt);
  }
In this implementation, subordinate index builds on alias.

@param parNode node needs to build subordinate index.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/schemafile/pagemgr/BTreePageManager.java