@Override
  protected String searchSubIndexAlias(int base, String alias, SchemaPageContext cxt)
      throws MetadataException, IOException {
    return getTargetLeafPage(getPageInstance(base, cxt), alias, cxt)
        .getAsAliasIndexPage()
        .getRecordByAlias(alias);
  }
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