@Override
public Comparable value(final ScoreDoc doc) {
return new ReverseComparable(_comparator.value(doc));
}
/** Computes the old-to-new permutation over the given comparator. */
private static Sorter.DocMap sort(final int maxDoc, DocComparator comparator) {
// check if the index is sorted
boolean sorted = true;
for (int i = 1; i < maxDoc; ++i) {
if (comparator.compare(i - 1, i) > 0) {
sorted = false;
break;
}
}
if (sorted) {
return null;
}
// sort doc IDs
final int[] docs = new int[maxDoc];
for (int i = 0; i < maxDoc; i++) {
docs[i] = i;
}
DocValueSorter sorter = new DocValueSorter(docs, comparator);
// It can be common to sort a reader, add docs, sort it again, ... and in
// that case timSort can save a lot of time
sorter.sort(0, docs.length); // docs is now the newToOld mapping
// The reason why we use MonotonicAppendingLongBuffer here is that it
// wastes very little memory if the index is in random order but can save
// a lot of memory if the index is already "almost" sorted
final PackedLongValues.Builder newToOldBuilder =
PackedLongValues.monotonicBuilder(PackedInts.COMPACT);
for (int i = 0; i < maxDoc; ++i) {
newToOldBuilder.add(docs[i]);
}
final PackedLongValues newToOld = newToOldBuilder.build();
for (int i = 0; i < maxDoc; ++i) {
docs[(int) newToOld.get(i)] = i;
} // docs is now the oldToNew mapping
final PackedLongValues.Builder oldToNewBuilder =
PackedLongValues.monotonicBuilder(PackedInts.COMPACT);
for (int i = 0; i < maxDoc; ++i) {
oldToNewBuilder.add(docs[i]);
}
final PackedLongValues oldToNew = oldToNewBuilder.build();
return new Sorter.DocMap() {
@Override
public int oldToNew(int docID) {
return (int) oldToNew.get(docID);
}
@Override
public int newToOld(int docID) {
return (int) newToOld.get(docID);
}
@Override
public int size() {
return maxDoc;
}
};
}
@Override
public int compare(ScoreDoc doc1, ScoreDoc doc2) {
return -_comparator.compare(doc1, doc2);
}