Class LimitedSortedDataBag

src/org/apache/pig/data/LimitedSortedDataBag.java:45–338

An ordered collection of Tuples (possibly) with multiples. Data is stored in a priority queue as it comes in, and only sorted when iterator is requested. LimitedSortedDataBag is not spillable. We allow a user defined comparator, but provide a default comparator in cases where the user doesn't spe

 * cases where the user doesn't specify one.
 */
public class LimitedSortedDataBag implements DataBag {

    private static final Log log = LogFactory.getLog(LimitedSortedDataBag.class);
    private static final long serialVersionUID = 1L;

    private final Comparator<Tuple> mComp;
	private final PriorityQueue<Tuple> priorityQ;
	private final long limit;

	/**
	 * @param comp Comparator to use to do the sorting.
	 * If null, DefaultComparator will be used.
	 */
	public LimitedSortedDataBag(Comparator<Tuple> comp, long limit) {
	    this.mComp = comp == null ? new DefaultComparator() : comp;
	    this.limit = limit;
	    this.priorityQ = new PriorityQueue<Tuple>(
	            (int)limit, getReversedComparator(mComp));
	}

	/**
     * Get the number of elements in the bag in memory.
     * @return number of elements in the bag
     */
	@Override
	public long size() {
	   return priorityQ.size();
	}

	/**
     * Find out if the bag is sorted.
     * @return true if this is a sorted data bag, false otherwise.
     */
	@Override
	public boolean isSorted() {
	    return true;
	}

	/**
     * Find out if the bag is distinct.
     * @return true if the bag is a distinct bag, false otherwise.
     */
	@Override
	public boolean isDistinct() {
	    return false;
	}

	/**
     * Get an iterator to the bag. For default and distinct bags,
     * no particular order is guaranteed. For sorted bags the order
     * is guaranteed to be sorted according
     * to the provided comparator.
     * @return tuple iterator
     */
	@Override
	public Iterator<Tuple> iterator() {
	    return new LimitedSortedDataBagIterator();
	}