docs/attachments/LUCENE-10373/LUCENE-10373.patch

diff --git a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/TaxonomyFacetSumIntAssociations.java b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/TaxonomyFacetSumIntAssociations.java
index 4827779375c..124bc43c134 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/TaxonomyFacetSumIntAssociations.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/TaxonomyFacetSumIntAssociations.java
@@ -48,8 +48,7 @@ public class TaxonomyFacetSumIntAssociations extends IntTaxonomyFacets {
     sumValues(fc.getMatchingDocs());
   }
 
-  private final void sumValues(List<MatchingDocs> matchingDocs) throws IOException {
-    // System.out.println("count matchingDocs=" + matchingDocs + " facetsField=" + facetsFieldName);
+  private void sumValues(List<MatchingDocs> matchingDocs) throws IOException {
     for (MatchingDocs hits : matchingDocs) {
       BinaryDocValues dv = hits.context.reader().getBinaryDocValues(indexFieldName);
       if (dv == null) { // this reader does not have DocValues for the requested category list
@@ -59,21 +58,43 @@ public class TaxonomyFacetSumIntAssociations extends IntTaxonomyFacets {
       DocIdSetIterator docs = hits.bits.iterator();
 
       int doc;
-      while ((doc = docs.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
-        if (dv.docID() < doc) {
-          dv.advance(doc);
+      if (values != null) {
+        while ((doc = docs.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
+          if (dv.docID() < doc) {
+            dv.advance(doc);
+          }
+          if (dv.docID() == doc) {
+            final BytesRef bytesRef = dv.binaryValue();
+            byte[] bytes = bytesRef.bytes;
+            int end = bytesRef.offset + bytesRef.length;
+            int offset = bytesRef.offset;
+            while (offset < end) {
+              int ord = (int) BitUtil.VH_BE_INT.get(bytes, offset);
+              offset += 4;
+              int value = (int) BitUtil.VH_BE_INT.get(bytes, offset);
+              offset += 4;
+              values[ord] += value;
+            }
+          }
         }
-        if (dv.docID() == doc) {
-          final BytesRef bytesRef = dv.binaryValue();
-          byte[] bytes = bytesRef.bytes;
-          int end = bytesRef.offset + bytesRef.length;
-          int offset = bytesRef.offset;
-          while (offset < end) {
-            int ord = (int) BitUtil.VH_BE_INT.get(bytes, offset);
-            offset += 4;
-            int value = (int) BitUtil.VH_BE_INT.get(bytes, offset);
-            offset += 4;
-            increment(ord, value);
+      } else {
+        assert sparseValues != null;
+        while ((doc = docs.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
+          if (dv.docID() < doc) {
+            dv.advance(doc);
+          }
+          if (dv.docID() == doc) {
+            final BytesRef bytesRef = dv.binaryValue();
+            byte[] bytes = bytesRef.bytes;
+            int end = bytesRef.offset + bytesRef.length;
+            int offset = bytesRef.offset;
+            while (offset < end) {
+              int ord = (int) BitUtil.VH_BE_INT.get(bytes, offset);
+              offset += 4;
+              int value = (int) BitUtil.VH_BE_INT.get(bytes, offset);
+              offset += 4;
+              sparseValues.addTo(ord, value);
+            }
           }
         }
       }