Package org.apache.lucene.search

Class DocIdSetIterator

java.lang.Object
org.apache.lucene.search.DocIdSetIterator
Direct Known Subclasses:
DocsEnum, FilteredDocIdSetIterator, FixedBitSet.FixedBitSetIterator, OpenBitSetIterator
public abstract class DocIdSetIterator extends Object
This abstract class defines methods to iterate over a set of non-decreasing doc ids. Note that this class assumes it iterates on doc Ids, and therefore NO_MORE_DOCS is set to 2147483647 in order to be used as a sentinel object. Implementations of this class are expected to consider Integer.MAX_VALUE as an invalid value.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    NO_MORE_DOCS
    When returned by nextDoc(), advance(int) and docID() it means there are no more docs in the iterator.

  • Constructor Summary

    Constructors
    Constructor
    Description
    DocIdSetIterator()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    abstract int
    advance(int target)
    Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself.
    abstract long
    cost()
    Returns the estimated cost of this DocIdSetIterator.
    abstract int
    docID()
    Returns the following: -1 or NO_MORE_DOCS if nextDoc() or advance(int) were not called yet.
    static final DocIdSetIterator
    empty()
    An empty DocIdSetIterator instance
    abstract int
    nextDoc()
    Advances to the next document in the set and returns the doc it is currently on, or NO_MORE_DOCS if there are no more docs in the set.
    NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.
    protected final int
    slowAdvance(int target)
    Slow (linear) implementation of advance(int) relying on nextDoc() to advance beyond the target position.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

    • DocIdSetIterator

      public DocIdSetIterator()

  • Method Details

    • empty

      public static final DocIdSetIterator empty()
      An empty DocIdSetIterator instance

    • docID

      public abstract int docID()
      Returns the following:

      Since:
      2.9

    • nextDoc

      public abstract int nextDoc() throws IOException
      Advances to the next document in the set and returns the doc it is currently on, or NO_MORE_DOCS if there are no more docs in the set.
      NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.
      Throws:
      IOException
      Since:
      2.9

    • advance

      public abstract int advance(int target) throws IOException
      Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself. Exhausts the iterator and returns NO_MORE_DOCS if target is greater than the highest document number in the set.

      The behavior of this method is undefined when called with target ≤ current, or after the iterator has exhausted. Both cases may result in unpredicted behavior.

      When target > current it behaves as if written: 

       int advance(int target) {
   int doc;
   while ((doc = nextDoc()) < target) {
   }
   return doc;
 }
      Some implementations are considerably more efficient than that.

      NOTE: this method may be called with NO_MORE_DOCS for efficiency by some Scorers. If your implementation cannot efficiently determine that it should exhaust, it is recommended that you check for that value in each call to this method.

      Throws:
      IOException
      Since:
      2.9

    • slowAdvance

      protected final int slowAdvance(int target) throws IOException
      Slow (linear) implementation of advance(int) relying on nextDoc() to advance beyond the target position.
      Throws:
      IOException

    • cost

      public abstract long cost()
      Returns the estimated cost of this DocIdSetIterator.

      This is generally an upper bound of the number of documents this iterator might match, but may be a rough heuristic, hardcoded value, or otherwise completely inaccurate.