org.apache.lucene.queries.intervals.IntervalIterator Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.queries.intervals;
import java.io.IOException;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.TwoPhaseIterator;
/**
* A {@link DocIdSetIterator} that also allows iteration over matching
* intervals in a document.
*
* Once the iterator is positioned on a document by calling {@link #advance(int)}
* or {@link #nextDoc()}, intervals may be retrieved by calling {@link #nextInterval()}
* until {@link #NO_MORE_INTERVALS} is returned.
*
* The limits of the current interval are returned by {@link #start()} and {@link #end()}.
* When the iterator has been moved to a new document, but before {@link #nextInterval()}
* has been called, both these methods return {@code -1}.
*
* Note that it is possible for a document to return {@link #NO_MORE_INTERVALS}
* on the first call to {@link #nextInterval()}
*/
public abstract class IntervalIterator extends DocIdSetIterator {
/**
* When returned from {@link #nextInterval()}, indicates that there are no more
* matching intervals on the current document
*/
public static final int NO_MORE_INTERVALS = Integer.MAX_VALUE;
/**
* The start of the current interval
*
* Returns -1 if {@link #nextInterval()} has not yet been called and {@link #NO_MORE_INTERVALS}
* once the iterator is exhausted.
*/
public abstract int start();
/**
* The end of the current interval
*
* Returns -1 if {@link #nextInterval()} has not yet been called and {@link #NO_MORE_INTERVALS}
* once the iterator is exhausted.
*/
public abstract int end();
/**
* The number of gaps within the current interval
*
* Note that this returns the number of gaps between the immediate sub-intervals
* of this interval, and does not include the gaps inside those sub-intervals.
*
* Should not be called before {@link #nextInterval()}, or after it has returned
* {@link #NO_MORE_INTERVALS}
*/
public abstract int gaps();
/**
* The width of the current interval
*/
public int width() {
return end() - start() + 1;
}
/**
* Advance the iterator to the next interval
*
* @return the start of the next interval, or {@link IntervalIterator#NO_MORE_INTERVALS} if
* there are no more intervals on the current document
*/
public abstract int nextInterval() throws IOException;
/**
* An indication of the average cost of iterating over all intervals in a document
*
* @see TwoPhaseIterator#matchCost()
*/
public abstract float matchCost();
@Override
public String toString() {
return docID() + ":[" + start() + "->" + end() + "]";
}
}