Support getMaxScore of DisjunctionSumScorer for non top level scoring…

… clause (#13066)

lucene/CHANGES.txt

@@ -211,6 +211,8 @@ Improvements
 
 * GITHUB#13156: Hunspell: don't proceed with other suggestions if we found good REP ones (Peter Gromov)
 
+* GITHUB#13066: Support getMaxScore of DisjunctionSumScorer for non top level scoring clause (Shintaro Murakami)
+
 Optimizations
 ---------------------
 

lucene/core/src/java/org/apache/lucene/search/DisjunctionSumScorer.java

@@ -18,10 +18,13 @@
 
 import java.io.IOException;
 import java.util.List;
+import org.apache.lucene.util.MathUtil;
 
 /** A Scorer for OR like queries, counterpart of <code>ConjunctionScorer</code>. */
 final class DisjunctionSumScorer extends DisjunctionScorer {
 
+  private final List<Scorer> scorers;
+
   /**
    * Construct a <code>DisjunctionScorer</code>.
    *
@@ -31,6 +34,7 @@ final class DisjunctionSumScorer extends DisjunctionScorer {
   DisjunctionSumScorer(Weight weight, List<Scorer> subScorers, ScoreMode scoreMode)
       throws IOException {
     super(weight, subScorers, scoreMode);
+    this.scorers = subScorers;
   }
 
   @Override
@@ -43,10 +47,25 @@ protected float score(DisiWrapper topList) throws IOException {
     return (float) score;
   }
 
+  @Override
+  public int advanceShallow(int target) throws IOException {
+    int min = DocIdSetIterator.NO_MORE_DOCS;
+    for (Scorer scorer : scorers) {
+      if (scorer.docID() <= target) {
+        min = Math.min(min, scorer.advanceShallow(target));
+      }
+    }
+    return min;
+  }
+
   @Override
   public float getMaxScore(int upTo) throws IOException {
-    // It's ok to return a bad upper bound here since we use WANDScorer when
-    // we actually care about block scores.
-    return Float.MAX_VALUE;
+    double maxScore = 0;
+    for (Scorer scorer : scorers) {
+      if (scorer.docID() <= upTo) {
+        maxScore += scorer.getMaxScore(upTo);
+      }
+    }
+    return (float) MathUtil.sumUpperBound(maxScore, scorers.size());
   }
 }

lucene/core/src/test/org/apache/lucene/search/TestBoolean2ScorerSupplier.java

@@ -536,5 +536,16 @@ public void testMaxScoreNonTopLevelScoringClause() throws Exception {
     Scorer scorer =
         new Boolean2ScorerSupplier(new FakeWeight(), subs, ScoreMode.TOP_SCORES, 0).get(10);
     assertEquals(2.0, scorer.getMaxScore(DocIdSetIterator.NO_MORE_DOCS), 0.0);
+
+    subs = new EnumMap<>(Occur.class);
+    for (Occur occur : Occur.values()) {
+      subs.put(occur, new ArrayList<>());
+    }
+
+    subs.get(Occur.SHOULD).add(clause1);
+    subs.get(Occur.SHOULD).add(clause2);
+
+    scorer = new Boolean2ScorerSupplier(new FakeWeight(), subs, ScoreMode.TOP_SCORES, 0).get(10);
+    assertEquals(2.0, scorer.getMaxScore(DocIdSetIterator.NO_MORE_DOCS), 0.0);
   }
 }