Class UnifiedHighlighter
- java.lang.Object
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- org.apache.lucene.search.uhighlight.UnifiedHighlighter
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public class UnifiedHighlighter extends Object
A Highlighter that can get offsets from either postings (IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
), term vectors (FieldType.setStoreTermVectorOffsets(boolean)
), or via re-analyzing text.This highlighter treats the single original document as the whole corpus, and then scores individual passages as if they were documents in this corpus. It uses a
BreakIterator
to find passages in the text; by default it breaks usinggetSentenceInstance(Locale.ROOT)
. It then iterates in parallel (merge sorting by offset) through the positions of all terms from the query, coalescing those hits that occur in a single passage into aPassage
, and then scores each Passage using a separatePassageScorer
. Passages are finally formatted into highlighted snippets with aPassageFormatter
.You can customize the behavior by calling some of the setters, or by subclassing and overriding some methods. Some important hooks:
getBreakIterator(String)
: Customize how the text is divided into passages.getScorer(String)
: Customize how passages are ranked.getFormatter(String)
: Customize how snippets are formatted.
This is thread-safe.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
UnifiedHighlighter.HighlightFlag
Flags for controlling highlighting behavior.protected static class
UnifiedHighlighter.LimitedStoredFieldVisitor
Fetches stored fields for highlighting.static class
UnifiedHighlighter.OffsetSource
Source of term offsets; essential for highlighting.
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Field Summary
Fields Modifier and Type Field Description static int
DEFAULT_CACHE_CHARS_THRESHOLD
static int
DEFAULT_MAX_LENGTH
protected FieldInfos
fieldInfos
protected Analyzer
indexAnalyzer
protected static char
MULTIVAL_SEP_CHAR
protected IndexSearcher
searcher
protected static CharacterRunAutomaton[]
ZERO_LEN_AUTOMATA_ARRAY
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Constructor Summary
Constructors Constructor Description UnifiedHighlighter(IndexSearcher indexSearcher, Analyzer indexAnalyzer)
Constructs the highlighter with the given index searcher and analyzer.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description protected static Set<Term>
extractTerms(Query query)
Extracts matching terms after rewriting against an empty indexprotected static BytesRef[]
filterExtractedTerms(Predicate<String> fieldMatcher, Set<Term> queryTerms)
protected CharacterRunAutomaton[]
getAutomata(String field, Query query, Set<UnifiedHighlighter.HighlightFlag> highlightFlags)
protected BreakIterator
getBreakIterator(String field)
Returns theBreakIterator
to use for dividing text into passages.int
getCacheFieldValCharsThreshold()
Limits the amount of field value pre-fetching until this threshold is passed.protected FieldHighlighter
getFieldHighlighter(String field, Query query, Set<Term> allTerms, int maxPassages)
protected FieldInfo
getFieldInfo(String field)
Called by the default implementation ofgetOffsetSource(String)
.protected Predicate<String>
getFieldMatcher(String field)
Returns the predicate to use for extracting the query part that must be highlighted.protected Set<UnifiedHighlighter.HighlightFlag>
getFlags(String field)
protected PassageFormatter
getFormatter(String field)
Returns thePassageFormatter
to use for formatting passages into highlighted snippets.Analyzer
getIndexAnalyzer()
...IndexSearcher
getIndexSearcher()
...int
getMaxLength()
The maximum content size to process.protected int
getMaxNoHighlightPassages(String field)
Returns the number of leading passages (as delineated by theBreakIterator
) when no highlights could be found.protected UnifiedHighlighter.OffsetSource
getOffsetSource(String field)
Determine the offset source for the specified field.protected FieldOffsetStrategy
getOffsetStrategy(UnifiedHighlighter.OffsetSource offsetSource, UHComponents components)
protected UnifiedHighlighter.OffsetSource
getOptimizedOffsetSource(String field, BytesRef[] terms, PhraseHelper phraseHelper, CharacterRunAutomaton[] automata)
protected PhraseHelper
getPhraseHelper(String field, Query query, Set<UnifiedHighlighter.HighlightFlag> highlightFlags)
protected PassageScorer
getScorer(String field)
Returns thePassageScorer
to use for ranking passages.String[]
highlight(String field, Query query, TopDocs topDocs)
Highlights the top passages from a single field.String[]
highlight(String field, Query query, TopDocs topDocs, int maxPassages)
Highlights the top-N passages from a single field.Map<String,String[]>
highlightFields(String[] fieldsIn, Query query, int[] docidsIn, int[] maxPassagesIn)
Highlights the top-N passages from multiple fields, for the provided int[] docids.Map<String,String[]>
highlightFields(String[] fields, Query query, TopDocs topDocs)
Highlights the top passages from multiple fields.Map<String,String[]>
highlightFields(String[] fields, Query query, TopDocs topDocs, int[] maxPassages)
Highlights the top-N passages from multiple fields.protected Map<String,Object[]>
highlightFieldsAsObjects(String[] fieldsIn, Query query, int[] docIdsIn, int[] maxPassagesIn)
Expert: highlights the top-N passages from multiple fields, for the provided int[] docids, to custom Object as returned by thePassageFormatter
.Object
highlightWithoutSearcher(String field, Query query, String content, int maxPassages)
Highlights text passed as a parameter.protected List<CharSequence[]>
loadFieldValues(String[] fields, DocIdSetIterator docIter, int cacheCharsThreshold)
Loads the String values for each docId by field to be highlighted.protected UnifiedHighlighter.LimitedStoredFieldVisitor
newLimitedStoredFieldsVisitor(String[] fields)
protected Collection<Query>
preSpanQueryRewrite(Query query)
When highlighting phrases accurately, we may need to handle custom queries that aren't supported in theWeightedSpanTermExtractor
as called by thePhraseHelper
.protected Boolean
requiresRewrite(SpanQuery spanQuery)
When highlighting phrases accurately, we need to know whichSpanQuery
's need to haveQuery.rewrite(IndexReader)
called on them.void
setBreakIterator(Supplier<BreakIterator> breakIterator)
void
setCacheFieldValCharsThreshold(int cacheFieldValCharsThreshold)
void
setFieldMatcher(Predicate<String> predicate)
void
setFormatter(PassageFormatter formatter)
void
setHandleMultiTermQuery(boolean handleMtq)
void
setHighlightPhrasesStrictly(boolean highlightPhrasesStrictly)
void
setMaxLength(int maxLength)
void
setMaxNoHighlightPassages(int defaultMaxNoHighlightPassages)
void
setScorer(PassageScorer scorer)
protected boolean
shouldHandleMultiTermQuery(String field)
Returns whetherMultiTermQuery
derivatives will be highlighted.protected boolean
shouldHighlightPhrasesStrictly(String field)
Returns whether position sensitive queries (e.g.protected boolean
shouldPreferPassageRelevancyOverSpeed(String field)
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Field Detail
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MULTIVAL_SEP_CHAR
protected static final char MULTIVAL_SEP_CHAR
- See Also:
- Constant Field Values
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DEFAULT_MAX_LENGTH
public static final int DEFAULT_MAX_LENGTH
- See Also:
- Constant Field Values
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DEFAULT_CACHE_CHARS_THRESHOLD
public static final int DEFAULT_CACHE_CHARS_THRESHOLD
- See Also:
- Constant Field Values
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ZERO_LEN_AUTOMATA_ARRAY
protected static final CharacterRunAutomaton[] ZERO_LEN_AUTOMATA_ARRAY
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searcher
protected final IndexSearcher searcher
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indexAnalyzer
protected final Analyzer indexAnalyzer
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fieldInfos
protected volatile FieldInfos fieldInfos
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Constructor Detail
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UnifiedHighlighter
public UnifiedHighlighter(IndexSearcher indexSearcher, Analyzer indexAnalyzer)
Constructs the highlighter with the given index searcher and analyzer.- Parameters:
indexSearcher
- Usually required, unlesshighlightWithoutSearcher(String, Query, String, int)
is used, in which case this needs to be null.indexAnalyzer
- Required, even if in some circumstances it isn't used.
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Method Detail
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extractTerms
protected static Set<Term> extractTerms(Query query) throws IOException
Extracts matching terms after rewriting against an empty index- Throws:
IOException
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setHandleMultiTermQuery
public void setHandleMultiTermQuery(boolean handleMtq)
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setHighlightPhrasesStrictly
public void setHighlightPhrasesStrictly(boolean highlightPhrasesStrictly)
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setMaxLength
public void setMaxLength(int maxLength)
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setBreakIterator
public void setBreakIterator(Supplier<BreakIterator> breakIterator)
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setScorer
public void setScorer(PassageScorer scorer)
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setFormatter
public void setFormatter(PassageFormatter formatter)
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setMaxNoHighlightPassages
public void setMaxNoHighlightPassages(int defaultMaxNoHighlightPassages)
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setCacheFieldValCharsThreshold
public void setCacheFieldValCharsThreshold(int cacheFieldValCharsThreshold)
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shouldHandleMultiTermQuery
protected boolean shouldHandleMultiTermQuery(String field)
Returns whetherMultiTermQuery
derivatives will be highlighted. By default it's enabled. MTQ highlighting can be expensive, particularly when using offsets in postings.
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shouldHighlightPhrasesStrictly
protected boolean shouldHighlightPhrasesStrictly(String field)
Returns whether position sensitive queries (e.g. phrases andSpanQuery
ies) should be highlighted strictly based on query matches (slower) versus any/all occurrences of the underlying terms. By default it's enabled, but there's no overhead if such queries aren't used.
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shouldPreferPassageRelevancyOverSpeed
protected boolean shouldPreferPassageRelevancyOverSpeed(String field)
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getFieldMatcher
protected Predicate<String> getFieldMatcher(String field)
Returns the predicate to use for extracting the query part that must be highlighted. By default only queries that target the current field are kept. (AKA requireFieldMatch)
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getMaxLength
public int getMaxLength()
The maximum content size to process. Content will be truncated to this size before highlighting. Typically snippets closer to the beginning of the document better summarize its content.
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getBreakIterator
protected BreakIterator getBreakIterator(String field)
Returns theBreakIterator
to use for dividing text into passages. This returnsBreakIterator.getSentenceInstance(Locale)
by default; subclasses can override to customize.Note: this highlighter will call
BreakIterator.preceding(int)
andBreakIterator.next()
many times on it. The default generic JDK implementation ofpreceding
performs poorly.
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getScorer
protected PassageScorer getScorer(String field)
Returns thePassageScorer
to use for ranking passages. This returns a newPassageScorer
by default; subclasses can override to customize.
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getFormatter
protected PassageFormatter getFormatter(String field)
Returns thePassageFormatter
to use for formatting passages into highlighted snippets. This returns a newPassageFormatter
by default; subclasses can override to customize.
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getMaxNoHighlightPassages
protected int getMaxNoHighlightPassages(String field)
Returns the number of leading passages (as delineated by theBreakIterator
) when no highlights could be found. If it's less than 0 (the default) then this defaults to themaxPassages
parameter given for each request. If this is 0 then the resulting highlight is null (not formatted).
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getCacheFieldValCharsThreshold
public int getCacheFieldValCharsThreshold()
Limits the amount of field value pre-fetching until this threshold is passed. The highlighter internally highlights in batches of documents sized on the sum field value length (in chars) of the fields to be highlighted (bounded bygetMaxLength()
for each field). By setting this to 0, you can force documents to be fetched and highlighted one at a time, which you usually shouldn't do. The default is 524288 chars which translates to about a megabyte. However, note that the highlighter sometimes ignores this and highlights one document at a time (without caching a bunch of documents in advance) when it can detect there's no point in it -- such as when all fields will be highlighted via re-analysis as one example.
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getIndexSearcher
public IndexSearcher getIndexSearcher()
... as passed in from constructor.
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getIndexAnalyzer
public Analyzer getIndexAnalyzer()
... as passed in from constructor.
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getOffsetSource
protected UnifiedHighlighter.OffsetSource getOffsetSource(String field)
Determine the offset source for the specified field. The default algorithm is as follows:- This calls
getFieldInfo(String)
. Note this returns null if there is no searcher or if the field isn't found there. - If there's a field info it has
IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
thenUnifiedHighlighter.OffsetSource.POSTINGS
is returned. - If there's a field info and
FieldInfo.hasVectors()
thenUnifiedHighlighter.OffsetSource.TERM_VECTORS
is returned (note we can't check here if the TV has offsets; if there isn't then an exception will get thrown down the line). - Fall-back:
UnifiedHighlighter.OffsetSource.ANALYSIS
is returned.
Note that the highlighter sometimes switches to something else based on the query, such as if you have
UnifiedHighlighter.OffsetSource.POSTINGS_WITH_TERM_VECTORS
but in fact don't need term vectors. - This calls
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getFieldInfo
protected FieldInfo getFieldInfo(String field)
Called by the default implementation ofgetOffsetSource(String)
. If there is no searcher then we simply always return null.
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highlight
public String[] highlight(String field, Query query, TopDocs topDocs) throws IOException
Highlights the top passages from a single field.- Parameters:
field
- field name to highlight. Must have a stored string value and also be indexed with offsets.query
- query to highlight.topDocs
- TopDocs containing the summary result documents to highlight.- Returns:
- Array of formatted snippets corresponding to the documents in
topDocs
. If no highlights were found for a document, the first sentence for the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlight
public String[] highlight(String field, Query query, TopDocs topDocs, int maxPassages) throws IOException
Highlights the top-N passages from a single field.- Parameters:
field
- field name to highlight. Must have a stored string value.query
- query to highlight.topDocs
- TopDocs containing the summary result documents to highlight.maxPassages
- The maximum number of top-N ranked passages used to form the highlighted snippets.- Returns:
- Array of formatted snippets corresponding to the documents in
topDocs
. If no highlights were found for a document, the firstmaxPassages
sentences from the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlightFields
public Map<String,String[]> highlightFields(String[] fields, Query query, TopDocs topDocs) throws IOException
Highlights the top passages from multiple fields.Conceptually, this behaves as a more efficient form of:
Map m = new HashMap(); for (String field : fields) { m.put(field, highlight(field, query, topDocs)); } return m;
- Parameters:
fields
- field names to highlight. Must have a stored string value.query
- query to highlight.topDocs
- TopDocs containing the summary result documents to highlight.- Returns:
- Map keyed on field name, containing the array of formatted snippets
corresponding to the documents in
topDocs
. If no highlights were found for a document, the first sentence from the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlightFields
public Map<String,String[]> highlightFields(String[] fields, Query query, TopDocs topDocs, int[] maxPassages) throws IOException
Highlights the top-N passages from multiple fields.Conceptually, this behaves as a more efficient form of:
Map m = new HashMap(); for (String field : fields) { m.put(field, highlight(field, query, topDocs, maxPassages)); } return m;
- Parameters:
fields
- field names to highlight. Must have a stored string value.query
- query to highlight.topDocs
- TopDocs containing the summary result documents to highlight.maxPassages
- The maximum number of top-N ranked passages per-field used to form the highlighted snippets.- Returns:
- Map keyed on field name, containing the array of formatted snippets
corresponding to the documents in
topDocs
. If no highlights were found for a document, the firstmaxPassages
sentences from the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlightFields
public Map<String,String[]> highlightFields(String[] fieldsIn, Query query, int[] docidsIn, int[] maxPassagesIn) throws IOException
Highlights the top-N passages from multiple fields, for the provided int[] docids.- Parameters:
fieldsIn
- field names to highlight. Must have a stored string value.query
- query to highlight.docidsIn
- containing the document IDs to highlight.maxPassagesIn
- The maximum number of top-N ranked passages per-field used to form the highlighted snippets.- Returns:
- Map keyed on field name, containing the array of formatted snippets
corresponding to the documents in
docidsIn
. If no highlights were found for a document, the firstmaxPassages
from the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlightFieldsAsObjects
protected Map<String,Object[]> highlightFieldsAsObjects(String[] fieldsIn, Query query, int[] docIdsIn, int[] maxPassagesIn) throws IOException
Expert: highlights the top-N passages from multiple fields, for the provided int[] docids, to custom Object as returned by thePassageFormatter
. Use this API to render to something other than String.- Parameters:
fieldsIn
- field names to highlight. Must have a stored string value.query
- query to highlight.docIdsIn
- containing the document IDs to highlight.maxPassagesIn
- The maximum number of top-N ranked passages per-field used to form the highlighted snippets.- Returns:
- Map keyed on field name, containing the array of formatted snippets
corresponding to the documents in
docIdsIn
. If no highlights were found for a document, the firstmaxPassages
from the field will be returned. - Throws:
IOException
- if an I/O error occurred during processingIllegalArgumentException
- iffield
was indexed withoutIndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS
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highlightWithoutSearcher
public Object highlightWithoutSearcher(String field, Query query, String content, int maxPassages) throws IOException
Highlights text passed as a parameter. This requires theIndexSearcher
provided to this highlighter is null. This use-case is more rare. Naturally, the mode of operation will beUnifiedHighlighter.OffsetSource.ANALYSIS
. The result of this method is whatever thePassageFormatter
returns. For theDefaultPassageFormatter
and assumingcontent
has non-zero length, the result will be a non-null string -- so it's safe to callObject.toString()
on it in that case.- Parameters:
field
- field name to highlight (as found in the query).query
- query to highlight.content
- text to highlight.maxPassages
- The maximum number of top-N ranked passages used to form the highlighted snippets.- Returns:
- result of the
PassageFormatter
-- probably a String. Might be null. - Throws:
IOException
- if an I/O error occurred during processing
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getFieldHighlighter
protected FieldHighlighter getFieldHighlighter(String field, Query query, Set<Term> allTerms, int maxPassages)
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filterExtractedTerms
protected static BytesRef[] filterExtractedTerms(Predicate<String> fieldMatcher, Set<Term> queryTerms)
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getFlags
protected Set<UnifiedHighlighter.HighlightFlag> getFlags(String field)
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getPhraseHelper
protected PhraseHelper getPhraseHelper(String field, Query query, Set<UnifiedHighlighter.HighlightFlag> highlightFlags)
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getAutomata
protected CharacterRunAutomaton[] getAutomata(String field, Query query, Set<UnifiedHighlighter.HighlightFlag> highlightFlags)
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getOptimizedOffsetSource
protected UnifiedHighlighter.OffsetSource getOptimizedOffsetSource(String field, BytesRef[] terms, PhraseHelper phraseHelper, CharacterRunAutomaton[] automata)
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getOffsetStrategy
protected FieldOffsetStrategy getOffsetStrategy(UnifiedHighlighter.OffsetSource offsetSource, UHComponents components)
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requiresRewrite
protected Boolean requiresRewrite(SpanQuery spanQuery)
When highlighting phrases accurately, we need to know whichSpanQuery
's need to haveQuery.rewrite(IndexReader)
called on them. It helps performance to avoid it if it's not needed. This method will be invoked on all SpanQuery instances recursively. If you have custom SpanQuery queries then override this to check instanceof and provide a definitive answer. If the query isn't your custom one, simply return null to have the default rules apply, which govern the ones included in Lucene.
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preSpanQueryRewrite
protected Collection<Query> preSpanQueryRewrite(Query query)
When highlighting phrases accurately, we may need to handle custom queries that aren't supported in theWeightedSpanTermExtractor
as called by thePhraseHelper
. Should custom query types be needed, this method should be overriden to return a collection of queries if appropriate, or null if nothing to do. If the query is not custom, simply returning null will allow the default rules to apply.- Parameters:
query
- Query to be highlighted- Returns:
- A Collection of Query object(s) if needs to be rewritten, otherwise null.
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loadFieldValues
protected List<CharSequence[]> loadFieldValues(String[] fields, DocIdSetIterator docIter, int cacheCharsThreshold) throws IOException
Loads the String values for each docId by field to be highlighted. By default this loads from stored fields by the same name as given, but a subclass can change the source. The returned Strings must be identical to what was indexed (at least for postings or term-vectors offset sources). This method must load fields for at least one document from the givenDocIdSetIterator
but need not return all of them; by default the character lengths are summed and this method will return early whencacheCharsThreshold
is exceeded. Specifically if that number is 0, then only one document is fetched no matter what. Values in the array ofCharSequence
will be null if no value was found.- Throws:
IOException
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newLimitedStoredFieldsVisitor
protected UnifiedHighlighter.LimitedStoredFieldVisitor newLimitedStoredFieldsVisitor(String[] fields)
- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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