public static void initializeFieldTrimmerClass(List<Class<? extends RelNode>> nodeClasses) {
    try {
      FIELD_TRIMMER_STATS.register(nodeClasses);
      FIELD_TRIMMER_NO_STATS.register(nodeClasses);
    } catch (Throwable t) {
      // LOG it but do not fail
      LOG.warn("Error initializing field trimmer instance", t);
    }
  }
This method can be called at startup time to pre-register all the
Hive classes that may be visited during the planning phase.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelFieldTrimmer.java