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FirstHitCollector.java
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FirstHitCollector.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.api.impl.index.collector;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.CollectionTerminatedException;
import org.apache.lucene.search.SimpleCollector;
import java.io.IOException;
/**
* A {@code Collector} that terminates the collection after the very first hit.
* As a consequence, additional collectors in this search that require a complete run over the index,
* such as {@code TotalHitCountCollector} or {@link DocValuesCollector}, won't work as expected.
*/
public final class FirstHitCollector extends SimpleCollector
{
public static final int NO_MATCH = -1;
private int result = NO_MATCH;
private int readerDocBase = 0;
/**
* @return true when this collector got a match, otherwise false.
*/
public boolean hasMatched()
{
return result != NO_MATCH;
}
/**
* @return the docId if this collector got a match, otherwise {@link FirstHitCollector#NO_MATCH}.
*/
public int getMatchedDoc()
{
return result;
}
@Override
public void collect( int doc ) throws IOException
{
result = readerDocBase + doc;
throw new CollectionTerminatedException();
}
@Override
public boolean needsScores()
{
return false;
}
@Override
protected void doSetNextReader( LeafReaderContext context ) throws IOException
{
super.doSetNextReader( context );
readerDocBase = context.docBase;
}
}