UnifiedHighlighter: new passageSortComparator option (#13276)

new 'passageSortComparator' option to allow sorting other than offset order

lucene/CHANGES.txt

@@ -298,6 +298,8 @@ Improvements
 * GITHUB#13385: Add Intervals.noIntervals() method to produce an empty IntervalsSource.
   (Aniketh Jain, Uwe Schindler, Alan Woodward))
 
+* GITHUB#13276: UnifiedHighlighter: new 'passageSortComparator' option to allow sorting other than offset order. (Seunghan Jung)
+
 Optimizations
 ---------------------
 

lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/FieldHighlighter.java

@@ -40,6 +40,7 @@ public class FieldHighlighter {
   protected final int maxPassages;
   protected final int maxNoHighlightPassages;
   protected final PassageFormatter passageFormatter;
+  protected final Comparator<Passage> passageSortComparator;
 
   public FieldHighlighter(
       String field,
@@ -48,7 +49,8 @@ public class FieldHighlighter {
       PassageScorer passageScorer,
       int maxPassages,
       int maxNoHighlightPassages,
-      PassageFormatter passageFormatter) {
+      PassageFormatter passageFormatter,
+      Comparator<Passage> passageSortComparator) {
     this.field = field;
     this.fieldOffsetStrategy = fieldOffsetStrategy;
     this.breakIterator = breakIterator;
@@ -56,6 +58,7 @@ public class FieldHighlighter {
     this.maxPassages = maxPassages;
     this.maxNoHighlightPassages = maxNoHighlightPassages;
     this.passageFormatter = passageFormatter;
+    this.passageSortComparator = passageSortComparator;
   }
 
   public String getField() {
@@ -191,8 +194,7 @@ public class FieldHighlighter {
     maybeAddPassage(passageQueue, passageScorer, passage, contentLength);
 
     Passage[] passages = passageQueue.toArray(new Passage[passageQueue.size()]);
-    // sort in ascending order
-    Arrays.sort(passages, Comparator.comparingInt(Passage::getStartOffset));
+    Arrays.sort(passages, passageSortComparator);
     return passages;
   }
 

lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/UnifiedHighlighter.java

@@ -21,6 +21,7 @@ import java.text.BreakIterator;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Comparator;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -86,6 +87,7 @@ import org.apache.lucene.util.InPlaceMergeSorter;
  *   <li>{@link #getBreakIterator(String)}: Customize how the text is divided into passages.
  *   <li>{@link #getScorer(String)}: Customize how passages are ranked.
  *   <li>{@link #getFormatter(String)}: Customize how snippets are formatted.
+ *   <li>{@link #getPassageSortComparator(String)}: Customize how snippets are formatted.
  * </ul>
  *
  * <p>This is thread-safe, notwithstanding the setters.
@@ -113,6 +115,8 @@ public class UnifiedHighlighter {
   private static final PassageScorer DEFAULT_PASSAGE_SCORER = new PassageScorer();
   private static final PassageFormatter DEFAULT_PASSAGE_FORMATTER = new DefaultPassageFormatter();
   private static final int DEFAULT_MAX_HIGHLIGHT_PASSAGES = -1;
+  private static final Comparator<Passage> DEFAULT_PASSAGE_SORT_COMPARATOR =
+      Comparator.comparingInt(Passage::getStartOffset);
 
   protected final IndexSearcher searcher; // if null, can only use highlightWithoutSearcher
 
@@ -151,6 +155,8 @@ public class UnifiedHighlighter {
 
   private int cacheFieldValCharsThreshold = DEFAULT_CACHE_CHARS_THRESHOLD;
 
+  private Comparator<Passage> passageSortComparator = DEFAULT_PASSAGE_SORT_COMPARATOR;
+
   /**
    * Constructs the highlighter with the given index searcher and analyzer.
    *
@@ -276,6 +282,7 @@ public class UnifiedHighlighter {
     private PassageFormatter formatter = DEFAULT_PASSAGE_FORMATTER;
     private int maxNoHighlightPassages = DEFAULT_MAX_HIGHLIGHT_PASSAGES;
     private int cacheFieldValCharsThreshold = DEFAULT_CACHE_CHARS_THRESHOLD;
+    private Comparator<Passage> passageSortComparator = DEFAULT_PASSAGE_SORT_COMPARATOR;
 
     /**
      * Constructor for UH builder which accepts {@link IndexSearcher} and {@link Analyzer} objects.
@@ -402,6 +409,11 @@ public class UnifiedHighlighter {
       return this;
     }
 
+    public Builder withPassageSortComparator(Comparator<Passage> value) {
+      this.passageSortComparator = value;
+      return this;
+    }
+
     public UnifiedHighlighter build() {
       return new UnifiedHighlighter(this);
     }
@@ -463,6 +475,7 @@ public class UnifiedHighlighter {
     this.formatter = builder.formatter;
     this.maxNoHighlightPassages = builder.maxNoHighlightPassages;
     this.cacheFieldValCharsThreshold = builder.cacheFieldValCharsThreshold;
+    this.passageSortComparator = builder.passageSortComparator;
   }
 
   /** Extracts matching terms */
@@ -614,6 +627,11 @@ public class UnifiedHighlighter {
     return formatter;
   }
 
+  /** Returns the {@link Comparator} to use for finally sorting passages. */
+  protected Comparator<Passage> getPassageSortComparator(String field) {
+    return passageSortComparator;
+  }
+
   /**
    * Returns the number of leading passages (as delineated by the {@link BreakIterator}) when no
    * highlights could be found. If it's less than 0 (the default) then this defaults to the {@code
@@ -1119,7 +1137,8 @@ public class UnifiedHighlighter {
         getScorer(field),
         maxPassages,
         getMaxNoHighlightPassages(field),
-        getFormatter(field));
+        getFormatter(field),
+        getPassageSortComparator(field));
   }
 
   protected FieldHighlighter newFieldHighlighter(
@@ -1129,7 +1148,8 @@ public class UnifiedHighlighter {
       PassageScorer passageScorer,
       int maxPassages,
       int maxNoHighlightPassages,
-      PassageFormatter passageFormatter) {
+      PassageFormatter passageFormatter,
+      Comparator<Passage> passageSortComparator) {
     return new FieldHighlighter(
         field,
         fieldOffsetStrategy,
@@ -1137,7 +1157,8 @@ public class UnifiedHighlighter {
         passageScorer,
         maxPassages,
         maxNoHighlightPassages,
-        passageFormatter);
+        passageFormatter,
+        passageSortComparator);
   }
 
   protected UHComponents getHighlightComponents(String field, Query query, Set<Term> allTerms) {

lucene/highlighter/src/test/org/apache/lucene/search/uhighlight/visibility/TestUnifiedHighlighterExtensibility.java

@@ -20,6 +20,7 @@ package org.apache.lucene.search.uhighlight.visibility;
 import java.io.IOException;
 import java.text.BreakIterator;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -129,6 +130,11 @@ public class TestUnifiedHighlighterExtensibility extends LuceneTestCase {
             return super.getFormatter(field);
           }
 
+          @Override
+          protected Comparator<Passage> getPassageSortComparator(String field) {
+            return super.getPassageSortComparator(field);
+          }
+
           @Override
           public Analyzer getIndexAnalyzer() {
             return super.getIndexAnalyzer();
@@ -186,7 +192,8 @@ public class TestUnifiedHighlighterExtensibility extends LuceneTestCase {
                 getScorer(field),
                 maxPassages,
                 getMaxNoHighlightPassages(field),
-                getFormatter(field));
+                getFormatter(field),
+                getPassageSortComparator(field));
           }
 
           @Override
@@ -240,7 +247,7 @@ public class TestUnifiedHighlighterExtensibility extends LuceneTestCase {
   public void testFieldHiglighterExtensibility() {
     final String fieldName = "fieldName";
     FieldHighlighter fieldHighlighter =
-        new FieldHighlighter(fieldName, null, null, null, 1, 1, null) {
+        new FieldHighlighter(fieldName, null, null, null, 1, 1, null, null) {
           @Override
           protected Passage[] highlightOffsetsEnums(OffsetsEnum offsetsEnums) throws IOException {
             return super.highlightOffsetsEnums(offsetsEnums);
@@ -262,7 +269,8 @@ public class TestUnifiedHighlighterExtensibility extends LuceneTestCase {
         PassageScorer passageScorer,
         int maxPassages,
         int maxNoHighlightPassages,
-        PassageFormatter passageFormatter) {
+        PassageFormatter passageFormatter,
+        Comparator<Passage> passageSortComparator) {
       super(
           field,
           fieldOffsetStrategy,
@@ -270,7 +278,8 @@ public class TestUnifiedHighlighterExtensibility extends LuceneTestCase {
           passageScorer,
           maxPassages,
           maxNoHighlightPassages,
-          passageFormatter);
+          passageFormatter,
+          passageSortComparator);
     }
 
     @Override