docs/attachments/LUCENE-8253/test-merge.patch

diff --git a/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterMerging.java b/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
index 6931efaed8..45d24fb781 100644
--- a/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
+++ b/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
@@ -24,6 +24,8 @@ import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.FieldType;
+import org.apache.lucene.document.NumericDocValuesField;
+import org.apache.lucene.document.StringField;
 import org.apache.lucene.document.TextField;
 import org.apache.lucene.index.IndexWriterConfig.OpenMode;
 import org.apache.lucene.store.AlreadyClosedException;
@@ -457,4 +459,28 @@ public class TestIndexWriterMerging extends LuceneTestCase {
 
     directory.close();
   }
+
+  public void testForceMergeDeletesWithSoftUpdates() throws Exception {
+    Directory dir = newDirectory();
+    IndexWriterConfig indexWriterConfig = newIndexWriterConfig()
+        .setSoftDeletesField("soft_delete")
+        .setMergePolicy(new LogByteSizeMergePolicy());
+    IndexWriter writer = new IndexWriter(dir, indexWriterConfig);
+    for (int i = 0; i < 2; i++) {
+      Document doc = new Document();
+      doc.add(new StringField("id", Integer.toString(i), Field.Store.YES));
+      writer.addDocument(doc);
+    }
+    writer.flush();
+    // the second segment includes only the tombstone
+    Document tombstone = new Document();
+    tombstone.add(new NumericDocValuesField("soft_delete", 1));
+    writer.softUpdateDocument(new Term("id", "1"), tombstone, new NumericDocValuesField("soft_delete", 1));
+    // LogByteSizeMergePolicy should merge these two segments as both have soft-deleted docs.
+    writer.forceMergeDeletes(true);
+    assertEquals(1, writer.segmentInfos.asList().size());
+    assertEquals(1, writer.maxDoc());
+    writer.close();
+    dir.close();
+  }
 }