@TestOnly
  public ISchemaPage getPageOnTest(int index) throws IOException, MetadataException {
    return ((PageManager) pageManager).getPageInstanceOnTest(index);
  }
TODO: shall merge with PageManager#reEstimateSegSize
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/schemafile/SchemaFile.java