public static SqlNode[] cloneArray(SqlNode[] nodes) {
   SqlNode[] clones = (SqlNode[]) nodes.clone();
   for (int i = 0; i < clones.length; i++) {
     SqlNode node = clones[i];
     if (node != null) {
       clones[i] = (SqlNode) node.clone();
     }
   }
   return clones;
 }