@Explain(vectorization = Vectorization.EXPRESSION, displayName = "predicateExpression", explainLevels = { Level.DEFAULT, Level.EXTENDED })
    public String getPredicateExpression() {
      return vectorFilterDesc.getPredicateExpression().toString();
    }
Some filters are generated or implied, which means it is not in the query.
It is added by the analyzer. For example, when we do an inner join, we add
filters to exclude those rows with null join key values.
ql/src/java/org/apache/hadoop/hive/ql/plan/FilterDesc.java