@Override
      public Void visitCall(RexCall call) {
        if (call.getKind() == SqlKind.CAST) {
          hasCast.set(true);
        }
        return super.visitCall(call);
      }
Extracts the non-null filter conditions from given filter node.

@param filter The filter condition to be checked.
@param join Join node whose right side has to be searched.
@return null : Anti join condition is not matched for filter.
        Empty list : No residual filter conditions present.
        Valid list containing the filter to be applied after join.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveAntiSemiJoinRule.java