Account soft-deletes in FrozenEngine (#51362)

Currently, we do not exclude soft-deleted documents
when opening index reader in the FrozenEngine.

Relates #50775
Backport of #51192

Author: dnhatn

x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/FrozenEngine.java

@@ -20,6 +20,7 @@
 import org.apache.lucene.index.NumericDocValues;
 import org.apache.lucene.index.PointValues;
 import org.apache.lucene.index.SegmentCommitInfo;
+import org.apache.lucene.index.SoftDeletesDirectoryReaderWrapper;
 import org.apache.lucene.index.SortedDocValues;
 import org.apache.lucene.index.SortedNumericDocValues;
 import org.apache.lucene.index.SortedSetDocValues;
@@ -76,7 +77,7 @@ public FrozenEngine(EngineConfig config) {
 
         boolean success = false;
         Directory directory = store.directory();
-        try (DirectoryReader reader = DirectoryReader.open(directory)) {
+        try (DirectoryReader reader = openDirectory(directory)) {
             canMatchReader = ElasticsearchDirectoryReader.wrap(new RewriteCachingDirectoryReader(directory, reader.leaves()),
                 config.getShardId());
             success = true;
@@ -89,6 +90,15 @@ public FrozenEngine(EngineConfig config) {
         }
     }
 
+    private DirectoryReader openDirectory(Directory directory) throws IOException {
+        final DirectoryReader reader = DirectoryReader.open(directory);
+        if (config().getIndexSettings().isSoftDeleteEnabled()) {
+            return new SoftDeletesDirectoryReaderWrapper(reader, Lucene.SOFT_DELETES_FIELD);
+        } else {
+            return reader;
+        }
+    }
+
     @Override
     protected DirectoryReader open(IndexCommit indexCommit) throws IOException {
         // we fake an empty DirectoryReader for the ReadOnlyEngine. this reader is only used
@@ -159,7 +169,7 @@ private synchronized DirectoryReader getOrOpenReader() throws IOException {
                 for (ReferenceManager.RefreshListener listeners : config ().getInternalRefreshListener()) {
                     listeners.beforeRefresh();
                 }
-                reader = DirectoryReader.open(engineConfig.getStore().directory());
+                reader = openDirectory(engineConfig.getStore().directory());
                 processReaders(reader, null);
                 reader = lastOpenedReader = wrapReader(reader, Function.identity());
                 reader.getReaderCacheHelper().addClosedListener(this::onReaderClosed);

x-pack/plugin/core/src/test/java/org/elasticsearch/index/engine/FrozenEngineTests.java

@@ -8,6 +8,7 @@
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.FilterDirectoryReader;
 import org.apache.lucene.index.NoMergePolicy;
+import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.ReferenceManager;
 import org.apache.lucene.search.TopDocs;
@@ -33,6 +34,8 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
+import static org.hamcrest.Matchers.equalTo;
+
 public class FrozenEngineTests extends EngineTestCase {
 
     public void testAcquireReleaseReset() throws IOException {
@@ -321,4 +324,32 @@ public void testCanMatch() throws IOException {
             }
         }
     }
+
+    public void testSearchers() throws Exception {
+        IOUtils.close(engine, store);
+        final AtomicLong globalCheckpoint = new AtomicLong(SequenceNumbers.NO_OPS_PERFORMED);
+        try (Store store = createStore()) {
+            EngineConfig config = config(defaultSettings, store, createTempDir(), newMergePolicy(), null, null, null,
+                globalCheckpoint::get, new NoneCircuitBreakerService());
+            final int totalDocs;
+            try (InternalEngine engine = createEngine(config)) {
+                applyOperations(engine, generateHistoryOnReplica(between(10, 1000), false, randomBoolean(), randomBoolean()));
+                globalCheckpoint.set(engine.getLocalCheckpoint());
+                engine.syncTranslog();
+                engine.flush();
+                engine.refresh("test");
+                try (Engine.Searcher engineSearcher = engine.acquireSearcher("test")) {
+                    final IndexSearcher searcher = new IndexSearcher(engineSearcher.getDirectoryReader());
+                    totalDocs = searcher.search(new MatchAllDocsQuery(), Integer.MAX_VALUE).scoreDocs.length;
+                }
+            }
+            try (FrozenEngine frozenEngine = new FrozenEngine(config)) {
+                try (Engine.Searcher engineSearcher = frozenEngine.acquireSearcher("test")) {
+                    IndexSearcher searcher = new IndexSearcher(engineSearcher.getDirectoryReader());
+                    TopDocs topDocs = searcher.search(new MatchAllDocsQuery(), Integer.MAX_VALUE);
+                    assertThat(topDocs.scoreDocs.length, equalTo(totalDocs));
+                }
+            }
+        }
+    }
 }