Class BitDocSet

solr/core/src/java/org/apache/solr/search/BitDocSet.java:33–346

A FixedBitSet based implementation of a DocSet. Good for medium/large sets. @since solr 0.9

 *
 * @since solr 0.9
 */
public class BitDocSet extends DocSet {
  // for the array object inside the FixedBitSet. long[] array won't change alignment, so no need to
  // calculate it.
  private static final long BASE_RAM_BYTES_USED =
      RamUsageEstimator.shallowSizeOfInstance(BitDocSet.class)
          + RamUsageEstimator.shallowSizeOfInstance(FixedBitSet.class)
          + RamUsageEstimator.NUM_BYTES_ARRAY_HEADER;

  // TODO consider SparseFixedBitSet alternative

  private final FixedBitSet bits;
  int size; // number of docs in the set (cached for perf)

  public BitDocSet() {
    bits = new FixedBitSet(64);
  }

  /** Construct a BitDocSet. The capacity of the {@link FixedBitSet} should be at least maxDoc() */
  public BitDocSet(FixedBitSet bits) {
    this.bits = bits;
    size = -1;
  }

  /**
   * Construct a BitDocSet, and provides the number of set bits. The capacity of the {@link
   * FixedBitSet} should be at least maxDoc()
   */
  public BitDocSet(FixedBitSet bits, int size) {
    this.bits = bits;
    this.size = size;
  }

  @Override
  public DocIterator iterator() {
    return new DocIterator() {
      private final BitSetIterator iter = new BitSetIterator(bits, 0L); // cost is not useful here
      private int pos = iter.nextDoc();

      @Override
      public boolean hasNext() {
        return pos != DocIdSetIterator.NO_MORE_DOCS;
      }

      @Override
      public Integer next() {
        return nextDoc();
      }

      @Override
      public void remove() {
        bits.clear(pos);
      }

      @Override
      public int nextDoc() {
        int old = pos;
        pos = iter.nextDoc();