org.apache.lucene.analysis.miscellaneous.UniqueTokenFilter Maven / Gradle / Ivy
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* the Apache License, Version 2.0 (the "License"); you may
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
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package org.apache.lucene.analysis.miscellaneous;
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 org.apache.lucene.analysis.util.CharArraySet;
import org.apache.lucene.util.Version;
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);
// use a fixed version, as we don't care about case sensitivity.
private final CharArraySet previous = new CharArraySet(Version.LUCENE_31, 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();
}
}