Checker createChecker(String pattern) {
    for (CheckerFactory checkerFactory : getCheckerFactories()) {
      Checker checker = checkerFactory.tryCreate(pattern);
      if (checker != null) {
        return checker;
      }
    }
    return null;
  }
Selects an optimized checker for a given string.
@param pattern
@return
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/AbstractFilterStringColLikeStringScalar.java