public ASTNode simpleBreadthFirstSearch(ASTNode ast, Collection<Integer> tokens) {
      int[] tokenArray = new int[tokens.size()];
      int i = 0;
      for (Integer token : tokens) {
        tokenArray[i] = token;
        ++i;
      }
      return simpleBreadthFirstSearch(ast, tokenArray);
    }
The context that doPhase1 uses to populate information pertaining to CBO
(currently, this is used for CTAS and insert-as-select).
ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java