org.apache.lucene.analysis.miscellaneous.UniqueTokenFilter Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of elasticsearch Show documentation
Show all versions of elasticsearch Show documentation
Elasticsearch subproject :server
/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.analysis.miscellaneous;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import java.io.IOException;
/**
* A token filter that generates unique tokens. Can remove unique tokens only on the same
* position increments as well.
*/
public class UniqueTokenFilter extends TokenFilter {
private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class);
private final PositionIncrementAttribute posIncAttribute = addAttribute(PositionIncrementAttribute.class);
private final CharArraySet previous = new CharArraySet(8, false);
private final boolean onlyOnSamePosition;
public UniqueTokenFilter(TokenStream in) {
this(in, false);
}
public UniqueTokenFilter(TokenStream in, boolean onlyOnSamePosition) {
super(in);
this.onlyOnSamePosition = onlyOnSamePosition;
}
@Override
public final boolean incrementToken() throws IOException {
while (input.incrementToken()) {
final char term[] = termAttribute.buffer();
final int length = termAttribute.length();
boolean duplicate;
if (onlyOnSamePosition) {
final int posIncrement = posIncAttribute.getPositionIncrement();
if (posIncrement > 0) {
previous.clear();
}
duplicate = (posIncrement == 0 && previous.contains(term, 0, length));
} else {
duplicate = previous.contains(term, 0, length);
}
// clone the term, and add to the set of seen terms.
char saved[] = new char[length];
System.arraycopy(term, 0, saved, 0, length);
previous.add(saved);
if (!duplicate) {
return true;
}
}
return false;
}
@Override
public final void reset() throws IOException {
super.reset();
previous.clear();
}
}