package org.apache.lucene.search;
/*
* 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.
*/
import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import org.apache.lucene.index.DocsAndPositionsEnum;
import org.apache.lucene.index.DocsEnum;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermState;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.index.FilteredTermsEnum;
import org.apache.lucene.util.Attribute;
import org.apache.lucene.util.AttributeImpl;
import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.UnicodeUtil;
import org.apache.lucene.util.automaton.Automaton;
import org.apache.lucene.util.automaton.BasicAutomata;
import org.apache.lucene.util.automaton.BasicOperations;
import org.apache.lucene.util.automaton.ByteRunAutomaton;
import org.apache.lucene.util.automaton.CompiledAutomaton;
import org.apache.lucene.util.automaton.LevenshteinAutomata;
/** Subclass of TermsEnum for enumerating all terms that are similar
* to the specified filter term.
*
* <p>Term enumerations are always ordered by
* {@link #getComparator}. Each term in the enumeration is
* greater than all that precede it.</p>
*/
public class FuzzyTermsEnum extends TermsEnum {
private TermsEnum actualEnum;
private BoostAttribute actualBoostAtt;
private final BoostAttribute boostAtt =
attributes().addAttribute(BoostAttribute.class);
private final MaxNonCompetitiveBoostAttribute maxBoostAtt;
private final LevenshteinAutomataAttribute dfaAtt;
private float bottom;
private BytesRef bottomTerm;
// TODO: chicken-and-egg
private final Comparator<BytesRef> termComparator = BytesRef.getUTF8SortedAsUnicodeComparator();
protected final float minSimilarity;
protected final float scale_factor;
protected final int termLength;
protected int maxEdits;
protected final boolean raw;
protected final Terms terms;
private final Term term;
protected final int termText[];
protected final int realPrefixLength;
private final boolean transpositions;
/**
* Constructor for enumeration of all terms from specified <code>reader</code> which share a prefix of
* length <code>prefixLength</code> with <code>term</code> and which have a fuzzy similarity >
* <code>minSimilarity</code>.
* <p>
* After calling the constructor the enumeration is already pointing to the first
* valid term if such a term exists.
*
* @param terms Delivers terms.
* @param atts {@link AttributeSource} created by the rewrite method of {@link MultiTermQuery}
* thats contains information about competitive boosts during rewrite. It is also used
* to cache DFAs between segment transitions.
* @param term Pattern term.
* @param minSimilarity Minimum required similarity for terms from the reader. Pass an integer value
* representing edit distance. Passing a fraction is deprecated.
* @param prefixLength Length of required common prefix. Default value is 0.
* @throws IOException if there is a low-level IO error
*/
public FuzzyTermsEnum(Terms terms, AttributeSource atts, Term term,
final float minSimilarity, final int prefixLength, boolean transpositions) throws IOException {
if (minSimilarity >= 1.0f && minSimilarity != (int)minSimilarity)
throw new IllegalArgumentException("fractional edit distances are not allowed");
if (minSimilarity < 0.0f)
throw new IllegalArgumentException("minimumSimilarity cannot be less than 0");
if(prefixLength < 0)
throw new IllegalArgumentException("prefixLength cannot be less than 0");
this.terms = terms;
this.term = term;
// convert the string into a utf32 int[] representation for fast comparisons
final String utf16 = term.text();
this.termText = new int[utf16.codePointCount(0, utf16.length())];
for (int cp, i = 0, j = 0; i < utf16.length(); i += Character.charCount(cp))
termText[j++] = cp = utf16.codePointAt(i);
this.termLength = termText.length;
this.dfaAtt = atts.addAttribute(LevenshteinAutomataAttribute.class);
//The prefix could be longer than the word.
//It's kind of silly though. It means we must match the entire word.
this.realPrefixLength = prefixLength > termLength ? termLength : prefixLength;
// if minSimilarity >= 1, we treat it as number of edits
if (minSimilarity >= 1f) {
this.minSimilarity = 0; // just driven by number of edits
maxEdits = (int) minSimilarity;
raw = true;
} else {
this.minSimilarity = minSimilarity;
// calculate the maximum k edits for this similarity
maxEdits = initialMaxDistance(this.minSimilarity, termLength);
raw = false;
}
if (transpositions && maxEdits > LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE) {
throw new UnsupportedOperationException("with transpositions enabled, distances > "
+ LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE + " are not supported ");
}
this.transpositions = transpositions;
this.scale_factor = 1.0f / (1.0f - this.minSimilarity);
this.maxBoostAtt = atts.addAttribute(MaxNonCompetitiveBoostAttribute.class);
bottom = maxBoostAtt.getMaxNonCompetitiveBoost();
bottomTerm = maxBoostAtt.getCompetitiveTerm();
bottomChanged(null, true);
}
/**
* return an automata-based enum for matching up to editDistance from
* lastTerm, if possible
*/
protected TermsEnum getAutomatonEnum(int editDistance, BytesRef lastTerm)
throws IOException {
final List<CompiledAutomaton> runAutomata = initAutomata(editDistance);
if (editDistance < runAutomata.size()) {
//if (BlockTreeTermsWriter.DEBUG) System.out.println("FuzzyTE.getAEnum: ed=" + editDistance + " lastTerm=" + (lastTerm==null ? "null" : lastTerm.utf8ToString()));
final CompiledAutomaton compiled = runAutomata.get(editDistance);
return new AutomatonFuzzyTermsEnum(terms.intersect(compiled, lastTerm == null ? null : compiled.floor(lastTerm, new BytesRef())),
runAutomata.subList(0, editDistance + 1).toArray(new CompiledAutomaton[editDistance + 1]));
} else {
return null;
}
}
/** initialize levenshtein DFAs up to maxDistance, if possible */
private List<CompiledAutomaton> initAutomata(int maxDistance) {
final List<CompiledAutomaton> runAutomata = dfaAtt.automata();
//System.out.println("cached automata size: " + runAutomata.size());
if (runAutomata.size() <= maxDistance &&
maxDistance <= LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE) {
LevenshteinAutomata builder =
new LevenshteinAutomata(UnicodeUtil.newString(termText, realPrefixLength, termText.length - realPrefixLength), transpositions);
for (int i = runAutomata.size(); i <= maxDistance; i++) {
Automaton a = builder.toAutomaton(i);
//System.out.println("compute automaton n=" + i);
// constant prefix
if (realPrefixLength > 0) {
Automaton prefix = BasicAutomata.makeString(
UnicodeUtil.newString(termText, 0, realPrefixLength));
a = BasicOperations.concatenate(prefix, a);
}
runAutomata.add(new CompiledAutomaton(a, true, false));
}
}
return runAutomata;
}
/** swap in a new actual enum to proxy to */
protected void setEnum(TermsEnum actualEnum) {
this.actualEnum = actualEnum;
this.actualBoostAtt = actualEnum.attributes().addAttribute(BoostAttribute.class);
}
/**
* fired when the max non-competitive boost has changed. this is the hook to
* swap in a smarter actualEnum
*/
private void bottomChanged(BytesRef lastTerm, boolean init)
throws IOException {
int oldMaxEdits = maxEdits;
// true if the last term encountered is lexicographically equal or after the bottom term in the PQ
boolean termAfter = bottomTerm == null || (lastTerm != null && termComparator.compare(lastTerm, bottomTerm) >= 0);
// as long as the max non-competitive boost is >= the max boost
// for some edit distance, keep dropping the max edit distance.
while (maxEdits > 0 && (termAfter ? bottom >= calculateMaxBoost(maxEdits) : bottom > calculateMaxBoost(maxEdits)))
maxEdits--;
if (oldMaxEdits != maxEdits || init) { // the maximum n has changed
maxEditDistanceChanged(lastTerm, maxEdits, init);
}
}
protected void maxEditDistanceChanged(BytesRef lastTerm, int maxEdits, boolean init)
throws IOException {
TermsEnum newEnum = getAutomatonEnum(maxEdits, lastTerm);
// instead of assert, we do a hard check in case someone uses our enum directly
// assert newEnum != null;
if (newEnum == null) {
assert maxEdits > LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE;
throw new IllegalArgumentException("maxEdits cannot be > LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE");
}
setEnum(newEnum);
}
// for some raw min similarity and input term length, the maximum # of edits
private int initialMaxDistance(float minimumSimilarity, int termLen) {
return (int) ((1D-minimumSimilarity) * termLen);
}
// for some number of edits, the maximum possible scaled boost
private float calculateMaxBoost(int nEdits) {
final float similarity = 1.0f - ((float) nEdits / (float) (termLength));
return (similarity - minSimilarity) * scale_factor;
}
private BytesRef queuedBottom = null;
@Override
public BytesRef next() throws IOException {
if (queuedBottom != null) {
bottomChanged(queuedBottom, false);
queuedBottom = null;
}
BytesRef term = actualEnum.next();
boostAtt.setBoost(actualBoostAtt.getBoost());
final float bottom = maxBoostAtt.getMaxNonCompetitiveBoost();
final BytesRef bottomTerm = maxBoostAtt.getCompetitiveTerm();
if (term != null && (bottom != this.bottom || bottomTerm != this.bottomTerm)) {
this.bottom = bottom;
this.bottomTerm = bottomTerm;
// clone the term before potentially doing something with it
// this is a rare but wonderful occurrence anyway
queuedBottom = BytesRef.deepCopyOf(term);
}
return term;
}
// proxy all other enum calls to the actual enum
@Override
public int docFreq() throws IOException {
return actualEnum.docFreq();
}
@Override
public long totalTermFreq() throws IOException {
return actualEnum.totalTermFreq();
}
@Override
public DocsEnum docs(Bits liveDocs, DocsEnum reuse, int flags) throws IOException {
return actualEnum.docs(liveDocs, reuse, flags);
}
@Override
public DocsAndPositionsEnum docsAndPositions(Bits liveDocs,
DocsAndPositionsEnum reuse, int flags) throws IOException {
return actualEnum.docsAndPositions(liveDocs, reuse, flags);
}
@Override
public void seekExact(BytesRef term, TermState state) throws IOException {
actualEnum.seekExact(term, state);
}
@Override
public TermState termState() throws IOException {
return actualEnum.termState();
}
@Override
public Comparator<BytesRef> getComparator() {
return actualEnum.getComparator();
}
@Override
public long ord() throws IOException {
return actualEnum.ord();
}
@Override
public boolean seekExact(BytesRef text) throws IOException {
return actualEnum.seekExact(text);
}
@Override
public SeekStatus seekCeil(BytesRef text) throws IOException {
return actualEnum.seekCeil(text);
}
@Override
public void seekExact(long ord) throws IOException {
actualEnum.seekExact(ord);
}
@Override
public BytesRef term() throws IOException {
return actualEnum.term();
}
/**
* Implement fuzzy enumeration with Terms.intersect.
* <p>
* This is the fastest method as opposed to LinearFuzzyTermsEnum:
* as enumeration is logarithmic to the number of terms (instead of linear)
* and comparison is linear to length of the term (rather than quadratic)
*/
private class AutomatonFuzzyTermsEnum extends FilteredTermsEnum {
private final ByteRunAutomaton matchers[];
private final BytesRef termRef;
private final BoostAttribute boostAtt =
attributes().addAttribute(BoostAttribute.class);
public AutomatonFuzzyTermsEnum(TermsEnum tenum, CompiledAutomaton compiled[]) {
super(tenum, false);
this.matchers = new ByteRunAutomaton[compiled.length];
for (int i = 0; i < compiled.length; i++)
this.matchers[i] = compiled[i].runAutomaton;
termRef = new BytesRef(term.text());
}
/** finds the smallest Lev(n) DFA that accepts the term. */
@Override
protected AcceptStatus accept(BytesRef term) {
//System.out.println("AFTE.accept term=" + term);
int ed = matchers.length - 1;
// we are wrapping either an intersect() TermsEnum or an AutomatonTermsENum,
// so we know the outer DFA always matches.
// now compute exact edit distance
while (ed > 0) {
if (matches(term, ed - 1)) {
ed--;
} else {
break;
}
}
//System.out.println("CHECK term=" + term.utf8ToString() + " ed=" + ed);
// scale to a boost and return (if similarity > minSimilarity)
if (ed == 0) { // exact match
boostAtt.setBoost(1.0F);
//System.out.println(" yes");
return AcceptStatus.YES;
} else {
final int codePointCount = UnicodeUtil.codePointCount(term);
final float similarity = 1.0f - ((float) ed / (float)
(Math.min(codePointCount, termLength)));
if (similarity > minSimilarity) {
boostAtt.setBoost((similarity - minSimilarity) * scale_factor);
//System.out.println(" yes");
return AcceptStatus.YES;
} else {
return AcceptStatus.NO;
}
}
}
/** returns true if term is within k edits of the query term */
final boolean matches(BytesRef term, int k) {
return k == 0 ? term.equals(termRef) : matchers[k].run(term.bytes, term.offset, term.length);
}
}
/** @lucene.internal */
public float getMinSimilarity() {
return minSimilarity;
}
/** @lucene.internal */
public float getScaleFactor() {
return scale_factor;
}
/**
* reuses compiled automata across different segments,
* because they are independent of the index
* @lucene.internal */
public static interface LevenshteinAutomataAttribute extends Attribute {
public List<CompiledAutomaton> automata();
}
/**
* Stores compiled automata as a list (indexed by edit distance)
* @lucene.internal */
public static final class LevenshteinAutomataAttributeImpl extends AttributeImpl implements LevenshteinAutomataAttribute {
private final List<CompiledAutomaton> automata = new ArrayList<CompiledAutomaton>();
@Override
public List<CompiledAutomaton> automata() {
return automata;
}
@Override
public void clear() {
automata.clear();
}
@Override
public int hashCode() {
return automata.hashCode();
}
@Override
public boolean equals(Object other) {
if (this == other)
return true;
if (!(other instanceof LevenshteinAutomataAttributeImpl))
return false;
return automata.equals(((LevenshteinAutomataAttributeImpl) other).automata);
}
@Override
public void copyTo(AttributeImpl target) {
final List<CompiledAutomaton> targetAutomata =
((LevenshteinAutomataAttribute) target).automata();
targetAutomata.clear();
targetAutomata.addAll(automata);
}
}
}