Rewrite SourceToParse with resolved docType (#36921)

We introduce a typeless API in #35790 where we translate the default
docType "_doc" to the user-defined docType. However, we do not rewrite
the SourceToParse with the resolved docType. This leads to a situation
where we have two translog operations for the same document with
different types:

- prvOp [Index{id='9LCpwGcBkJN7eZxaB54L', type='_doc', seqNo=1,
  primaryTerm=1, version=1, autoGeneratedIdTimestamp=1545125562123}]

- newOp [Index{id='9LCpwGcBkJN7eZxaB54L', type='not_doc', seqNo=1,
  primaryTerm=1, version=1, autoGeneratedIdTimestamp=-1}]

Closes #36769

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -710,9 +710,17 @@ public class IndexShard extends AbstractIndexShardComponent implements IndicesCl
         ensureWriteAllowed(origin);
         Engine.Index operation;
         try {
-            operation = prepareIndex(docMapper(sourceToParse.type()), indexSettings.getIndexVersionCreated(), sourceToParse, seqNo,
-                opPrimaryTerm, version, versionType, origin, autoGeneratedTimeStamp, isRetry,
-                ifSeqNo, ifPrimaryTerm);
+            final String resolvedType = resolveType(sourceToParse.type());
+            final SourceToParse sourceWithResolvedType;
+            if (resolvedType.equals(sourceToParse.type())) {
+                sourceWithResolvedType = sourceToParse;
+            } else {
+                sourceWithResolvedType = SourceToParse.source(sourceToParse.index(), resolvedType, sourceToParse.id(),
+                    sourceToParse.source(), sourceToParse.getXContentType());
+                sourceWithResolvedType.routing(sourceToParse.routing());
+            }
+            operation = prepareIndex(docMapper(resolvedType), indexSettings.getIndexVersionCreated(), sourceWithResolvedType,
+                seqNo, opPrimaryTerm, version, versionType, origin, autoGeneratedTimeStamp, isRetry, ifSeqNo, ifPrimaryTerm);
             Mapping update = operation.parsedDoc().dynamicMappingsUpdate();
             if (update != null) {
                 return new Engine.IndexResult(update);

server/src/test/java/org/elasticsearch/index/shard/IndexShardIT.java

@@ -64,6 +64,7 @@ import org.elasticsearch.index.engine.SegmentsStats;
 import org.elasticsearch.index.flush.FlushStats;
 import org.elasticsearch.index.mapper.SourceToParse;
 import org.elasticsearch.index.seqno.SequenceNumbers;
+import org.elasticsearch.index.translog.TestTranslog;
 import org.elasticsearch.index.translog.Translog;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.indices.breaker.CircuitBreakerService;
@@ -862,4 +863,28 @@ public class IndexShardIT extends ESSingleNodeTestCase {
             client().search(countRequest).actionGet().getHits().getTotalHits().value, equalTo(numDocs + moreDocs));
     }
 
+    public void testShardChangesWithDefaultDocType() throws Exception {
+        Settings settings = Settings.builder()
+            .put("index.number_of_shards", 1)
+            .put("index.number_of_replicas", 0)
+            .put("index.translog.flush_threshold_size", "512mb") // do not flush
+            .put("index.soft_deletes.enabled", true).build();
+        IndexService indexService = createIndex("index", settings, "user_doc", "title", "type=keyword");
+        int numOps = between(1, 10);
+        for (int i = 0; i < numOps; i++) {
+            if (randomBoolean()) {
+                client().prepareIndex("index", randomFrom("_doc", "user_doc"), randomFrom("1", "2"))
+                    .setSource("{}", XContentType.JSON).get();
+            } else {
+                client().prepareDelete("index", randomFrom("_doc", "user_doc"), randomFrom("1", "2")).get();
+            }
+        }
+        IndexShard shard = indexService.getShard(0);
+        try (Translog.Snapshot luceneSnapshot = shard.newChangesSnapshot("test", 0, numOps - 1, true);
+             Translog.Snapshot translogSnapshot = getTranslog(shard).newSnapshot()) {
+            List<Translog.Operation> opsFromLucene = TestTranslog.drainSnapshot(luceneSnapshot, true);
+            List<Translog.Operation> opsFromTranslog = TestTranslog.drainSnapshot(translogSnapshot, true);
+            assertThat(opsFromLucene, equalTo(opsFromTranslog));
+        }
+    }
 }

server/src/test/java/org/elasticsearch/index/translog/TestTranslog.java

@@ -34,7 +34,9 @@ import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Random;
 import java.util.Set;
@@ -128,4 +130,16 @@ public class TestTranslog {
     public static long getCurrentTerm(Translog translog) {
         return translog.getCurrent().getPrimaryTerm();
     }
+
+    public static List<Translog.Operation> drainSnapshot(Translog.Snapshot snapshot, boolean sortBySeqNo) throws IOException {
+        final List<Translog.Operation> ops = new ArrayList<>(snapshot.totalOperations());
+        Translog.Operation op;
+        while ((op = snapshot.next()) != null) {
+            ops.add(op);
+        }
+        if (sortBySeqNo) {
+            ops.sort(Comparator.comparing(Translog.Operation::seqNo));
+        }
+        return ops;
+    }
 }