/*
* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
* compatible open source license.
*/
/*
* 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
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/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*/
package org.apache.lucene.search.uhighlight;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.queries.spans.SpanMultiTermQueryWrapper;
import org.apache.lucene.queries.spans.SpanNearQuery;
import org.apache.lucene.queries.spans.SpanOrQuery;
import org.apache.lucene.queries.spans.SpanQuery;
import org.apache.lucene.queries.spans.SpanTermQuery;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.PrefixQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.BytesRef;
import org.opensearch.common.CheckedSupplier;
import org.opensearch.common.Nullable;
import org.opensearch.common.lucene.search.MultiPhrasePrefixQuery;
import org.opensearch.index.IndexSettings;
import java.io.IOException;
import java.text.BreakIterator;
import java.util.Collection;
import java.util.Collections;
import java.util.Locale;
import java.util.Set;
import java.util.function.Predicate;
/**
* Subclass of the {@link UnifiedHighlighter} that works for a single field in a single document.
* Uses a custom {@link PassageFormatter}. Accepts field content as a constructor
* argument, given that loadings field value can be done reading from _source field.
* Supports using different {@link BreakIterator} to break the text into fragments. Considers every distinct field
* value as a discrete passage for highlighting (unless the whole content needs to be highlighted).
* Supports both returning empty snippets and non highlighted snippets when no highlighting can be performed.
*/
public class CustomUnifiedHighlighter extends UnifiedHighlighter {
public static final char MULTIVAL_SEP_CHAR = (char) 0;
private static final Snippet[] EMPTY_SNIPPET = new Snippet[0];
private final OffsetSource offsetSource;
private final PassageFormatter passageFormatter;
private final BreakIterator breakIterator;
private final String index;
private final String field;
private final Locale breakIteratorLocale;
private final int noMatchSize;
private final FieldHighlighter fieldHighlighter;
private final int maxAnalyzedOffset;
private final Integer fieldMaxAnalyzedOffset;
/**
* Creates a new instance of {@link CustomUnifiedHighlighter}
*
* @param analyzer the analyzer used for the field at index time, used for multi term queries internally.
* @param offsetSource the {@link OffsetSource} to used for offsets retrieval.
* @param passageFormatter our own {@link CustomPassageFormatter}
* which generates snippets in forms of {@link Snippet} objects.
* @param breakIteratorLocale the {@link Locale} to use for dividing text into passages.
* If null {@link Locale#ROOT} is used.
* @param breakIterator the {@link BreakIterator} to use for dividing text into passages.
* If null {@link BreakIterator#getSentenceInstance(Locale)} is used.
* @param index the index we're highlighting, mostly used for error messages
* @param field the name of the field we're highlighting
* @param query the query we're highlighting
* @param noMatchSize The size of the text that should be returned when no highlighting can be performed.
* @param maxPassages the maximum number of passes to highlight
* @param fieldMatcher decides which terms should be highlighted
* @param maxAnalyzedOffset if the field is more than this long we'll refuse to use the ANALYZED
* offset source for it because it'd be super slow
* @param fieldMaxAnalyzedOffset this is used to limit the length of input that will be ANALYZED, this allows bigger fields to be partially highligthed
*/
public CustomUnifiedHighlighter(
IndexSearcher searcher,
Analyzer analyzer,
OffsetSource offsetSource,
PassageFormatter passageFormatter,
@Nullable Locale breakIteratorLocale,
@Nullable BreakIterator breakIterator,
String index,
String field,
Query query,
int noMatchSize,
int maxPassages,
Predicate<String> fieldMatcher,
int maxAnalyzedOffset,
Integer fieldMaxAnalyzedOffset
) throws IOException {
super(searcher, analyzer);
this.offsetSource = offsetSource;
this.breakIterator = breakIterator;
this.breakIteratorLocale = breakIteratorLocale == null ? Locale.ROOT : breakIteratorLocale;
this.passageFormatter = passageFormatter;
this.index = index;
this.field = field;
this.noMatchSize = noMatchSize;
this.setFieldMatcher(fieldMatcher);
this.maxAnalyzedOffset = maxAnalyzedOffset;
fieldHighlighter = getFieldHighlighter(field, query, extractTerms(query), maxPassages);
this.fieldMaxAnalyzedOffset = fieldMaxAnalyzedOffset;
}
/**
* Highlights the field value.
*/
public Snippet[] highlightField(LeafReader reader, int docId, CheckedSupplier<String, IOException> loadFieldValue) throws IOException {
if (fieldHighlighter.fieldOffsetStrategy == NoOpOffsetStrategy.INSTANCE && noMatchSize == 0) {
// If the query is such that there can't possibly be any matches then skip doing *everything*
return EMPTY_SNIPPET;
}
String fieldValue = loadFieldValue.get();
if (fieldValue == null) {
return null;
}
int fieldValueLength = fieldValue.length();
if (fieldMaxAnalyzedOffset != null && fieldMaxAnalyzedOffset > maxAnalyzedOffset) {
throw new IllegalArgumentException(
"max_analyzer_offset has exceeded ["
+ maxAnalyzedOffset
+ "] - maximum allowed to be analyzed for highlighting. "
+ "This maximum can be set by changing the ["
+ IndexSettings.MAX_ANALYZED_OFFSET_SETTING.getKey()
+ "] index level setting. "
+ "For large texts, indexing with offsets or term vectors is recommended!"
);
}
// if fieldMaxAnalyzedOffset is not defined
// and if this happens we should fallback to the previous behavior
if ((offsetSource == OffsetSource.ANALYSIS) && (fieldValueLength > maxAnalyzedOffset && fieldMaxAnalyzedOffset == null)) {
throw new IllegalArgumentException(
"The length of ["
+ field
+ "] field of ["
+ docId
+ "] doc of ["
+ index
+ "] index "
+ "has exceeded ["
+ maxAnalyzedOffset
+ "] - maximum allowed to be analyzed for highlighting. "
+ "This maximum can be set by changing the ["
+ IndexSettings.MAX_ANALYZED_OFFSET_SETTING.getKey()
+ "] index level setting. "
+ "For large texts, indexing with offsets or term vectors is recommended!"
);
}
Snippet[] result = (Snippet[]) fieldHighlighter.highlightFieldForDoc(reader, docId, fieldValue);
return result == null ? EMPTY_SNIPPET : result;
}
@Override
protected BreakIterator getBreakIterator(String field) {
return breakIterator;
}
public PassageFormatter getFormatter() {
return passageFormatter;
}
@Override
protected PassageFormatter getFormatter(String field) {
return passageFormatter;
}
@Override
protected FieldHighlighter getFieldHighlighter(String field, Query query, Set<Term> allTerms, int maxPassages) {
Predicate<String> fieldMatcher = getFieldMatcher(field);
BytesRef[] terms = filterExtractedTerms(fieldMatcher, allTerms);
Set<HighlightFlag> highlightFlags = getFlags(field);
PhraseHelper phraseHelper = getPhraseHelper(field, query, highlightFlags);
LabelledCharArrayMatcher[] automata = getAutomata(field, query, highlightFlags);
UHComponents components = new UHComponents(field, fieldMatcher, query, terms, phraseHelper, automata, false, highlightFlags);
OffsetSource offsetSource = getOptimizedOffsetSource(components);
BreakIterator breakIterator = new SplittingBreakIterator(getBreakIterator(field), UnifiedHighlighter.MULTIVAL_SEP_CHAR);
FieldOffsetStrategy strategy = getOffsetStrategy(offsetSource, components);
return new CustomFieldHighlighter(
field,
strategy,
breakIteratorLocale,
breakIterator,
getScorer(field),
maxPassages,
(noMatchSize > 0 ? 1 : 0),
getFormatter(field),
noMatchSize
);
}
@Override
protected Collection<Query> preSpanQueryRewrite(Query query) {
return rewriteCustomQuery(query);
}
/**
* Translate custom queries in queries that are supported by the unified highlighter.
*/
private Collection<Query> rewriteCustomQuery(Query query) {
if (query instanceof MultiPhrasePrefixQuery) {
MultiPhrasePrefixQuery mpq = (MultiPhrasePrefixQuery) query;
Term[][] terms = mpq.getTerms();
int[] positions = mpq.getPositions();
SpanQuery[] positionSpanQueries = new SpanQuery[positions.length];
int sizeMinus1 = terms.length - 1;
for (int i = 0; i < positions.length; i++) {
SpanQuery[] innerQueries = new SpanQuery[terms[i].length];
for (int j = 0; j < terms[i].length; j++) {
if (i == sizeMinus1) {
innerQueries[j] = new SpanMultiTermQueryWrapper<>(new PrefixQuery(terms[i][j]));
} else {
innerQueries[j] = new SpanTermQuery(terms[i][j]);
}
}
if (innerQueries.length > 1) {
positionSpanQueries[i] = new SpanOrQuery(innerQueries);
} else {
positionSpanQueries[i] = innerQueries[0];
}
}
if (positionSpanQueries.length == 1) {
return Collections.singletonList(positionSpanQueries[0]);
}
// sum position increments beyond 1
int positionGaps = 0;
if (positions.length >= 2) {
// positions are in increasing order. max(0,...) is just a safeguard.
positionGaps = Math.max(0, positions[positions.length - 1] - positions[0] - positions.length + 1);
}
// if original slop is 0 then require inOrder
boolean inorder = (mpq.getSlop() == 0);
return Collections.singletonList(new SpanNearQuery(positionSpanQueries, mpq.getSlop() + positionGaps, inorder));
} else {
return null;
}
}
/**
* Forces the offset source for this highlighter
*/
@Override
protected OffsetSource getOffsetSource(String field) {
if (offsetSource == null) {
return super.getOffsetSource(field);
}
return offsetSource;
}
/** Customize the highlighting flags to use by field. */
@Override
protected Set<HighlightFlag> getFlags(String field) {
final Set<HighlightFlag> flags = super.getFlags(field);
// Change the defaults introduced by https://issues.apache.org/jira/browse/LUCENE-9431
flags.remove(HighlightFlag.WEIGHT_MATCHES);
return flags;
}
}