private String getOptimizedByCboInfo() {
    String ruleExclusionRegex = conf.get(ConfVars.HIVE_CBO_RULE_EXCLUSION_REGEX.varname, "");
    String cboInfo = "Plan optimized by CBO.";
    if (!ruleExclusionRegex.isEmpty()) {
      cboInfo = cboInfo + (" " + EXCLUDED_RULES_PREFIX + ruleExclusionRegex);
    }
    return cboInfo;
  }
This method is useful if we want to obtain the logical plan after being parsed and
optimized by Calcite.

@return the Calcite plan for the query, null if it could not be generated
ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java