protected IndexPredicateAnalyzer.FieldValidator getFieldValidator() {
    return null;
  }
Get an optional {@link IndexPredicateAnalyzer.FieldValidator validator}. A validator can be
used to optinally filter out the predicates which need not be decomposed. By default this
method returns {@code null} which means that all predicates are pushed but consumers can choose
to override this to provide a custom validator as well.
hbase-handler/src/java/org/apache/hadoop/hive/hbase/AbstractHBaseKeyPredicateDecomposer.java