@Override
    public Void visitFieldAccess(RexFieldAccess fieldAccess) {
      throw new Util.FoundOne(fieldAccess);
    }
Given a list of predicates to push down, this methods returns the set of predicates
that still need to be pushed. Predicates need to be pushed because 1) their String
representation is not included in input set of predicates to exclude, or 2) they are
already in the subtree rooted at the input node.
This method updates the set of predicates to exclude with the String representation
of the predicates in the output and in the subtree.

@param predicatesToExclude String representation of predicates that should be excluded
@param inp root of the subtree
@param predsToPushDown candidate predicates to push down through the subtree
@return list of predicates to push down
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/HiveCalciteUtil.java