Add index version check retrospectively.

server/src/main/java/org/elasticsearch/index/IndexVersions.java

@@ -180,6 +180,7 @@ private static Version parseUnchecked(String version) {
     public static final IndexVersion SPARSE_VECTOR_PRUNING_INDEX_OPTIONS_SUPPORT = def(9_031_0_00, Version.LUCENE_10_2_2);
     public static final IndexVersion DEFAULT_DENSE_VECTOR_TO_BBQ_HNSW = def(9_032_0_00, Version.LUCENE_10_2_2);
     public static final IndexVersion MATCH_ONLY_TEXT_STORED_AS_BYTES = def(9_033_0_00, Version.LUCENE_10_2_2);
+    public static final IndexVersion USE_819_TSDB_DOC_VALUES_FORMAT = def(9_034_0_00, Version.LUCENE_10_2_2);
 
     /*
      * STOP! READ THIS FIRST! No, really,

server/src/main/java/org/elasticsearch/index/codec/PerFieldFormatSupplier.java

@@ -20,6 +20,7 @@
 import org.elasticsearch.index.IndexVersions;
 import org.elasticsearch.index.codec.bloomfilter.ES87BloomFilterPostingsFormat;
 import org.elasticsearch.index.codec.postings.ES812PostingsFormat;
+import org.elasticsearch.index.codec.tsdb.ES87TSDBDocValuesFormat;
 import org.elasticsearch.index.codec.tsdb.es819.ES819TSDBDocValuesFormat;
 import org.elasticsearch.index.mapper.CompletionFieldMapper;
 import org.elasticsearch.index.mapper.IdFieldMapper;
@@ -35,14 +36,16 @@ public class PerFieldFormatSupplier {
 
     private static final DocValuesFormat docValuesFormat = new Lucene90DocValuesFormat();
     private static final KnnVectorsFormat knnVectorsFormat = new Lucene99HnswVectorsFormat();
-    private static final ES819TSDBDocValuesFormat tsdbDocValuesFormat = new ES819TSDBDocValuesFormat();
+    private static final ES87TSDBDocValuesFormat es87TsdbDocValuesFormat = new ES87TSDBDocValuesFormat();
+    private static final ES819TSDBDocValuesFormat es819TsdbDocValuesFormat = new ES819TSDBDocValuesFormat();
     private static final ES812PostingsFormat es812PostingsFormat = new ES812PostingsFormat();
     private static final PostingsFormat completionPostingsFormat = PostingsFormat.forName("Completion101");
 
     private final ES87BloomFilterPostingsFormat bloomFilterPostingsFormat;
     private final MapperService mapperService;
 
     private final PostingsFormat defaultPostingsFormat;
+    private final DocValuesFormat defaultTsdbDocValuesFormat;
 
     public PerFieldFormatSupplier(MapperService mapperService, BigArrays bigArrays) {
         this.mapperService = mapperService;
@@ -56,6 +59,12 @@ public PerFieldFormatSupplier(MapperService mapperService, BigArrays bigArrays)
             // our own posting format using PFOR
             defaultPostingsFormat = es812PostingsFormat;
         }
+        if (mapperService != null
+            && mapperService.getIndexSettings().getIndexVersionCreated().onOrAfter(IndexVersions.USE_819_TSDB_DOC_VALUES_FORMAT)) {
+            defaultTsdbDocValuesFormat = es819TsdbDocValuesFormat;
+        } else {
+            defaultTsdbDocValuesFormat = es87TsdbDocValuesFormat;
+        }
     }
 
     public PostingsFormat getPostingsFormatForField(String field) {
@@ -106,7 +115,7 @@ public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
 
     public DocValuesFormat getDocValuesFormatForField(String field) {
         if (useTSDBDocValuesFormat(field)) {
-            return tsdbDocValuesFormat;
+            return defaultTsdbDocValuesFormat;
         }
         return docValuesFormat;
     }

server/src/main/java/org/elasticsearch/index/codec/tsdb/ES87TSDBDocValuesFormat.java

@@ -93,7 +93,7 @@ public ES87TSDBDocValuesFormat(int skipIndexIntervalSize) {
 
     @Override
     public DocValuesConsumer fieldsConsumer(SegmentWriteState state) throws IOException {
-        throw new UnsupportedOperationException("writing es87 doc values is no longer supported");
+        return new ES87TSDBDocValuesConsumer(state, skipIndexIntervalSize, DATA_CODEC, DATA_EXTENSION, META_CODEC, META_EXTENSION);
     }
 
     @Override

server/src/main/java/org/elasticsearch/index/codec/tsdb/es819/ES819TSDBDocValuesFormat.java

@@ -14,6 +14,8 @@
 import org.apache.lucene.index.SegmentReadState;
 import org.apache.lucene.index.SegmentWriteState;
 import org.elasticsearch.core.SuppressForbidden;
+import org.elasticsearch.index.IndexVersion;
+import org.elasticsearch.index.IndexVersions;
 
 import java.io.IOException;
 
@@ -139,4 +141,9 @@ public DocValuesConsumer fieldsConsumer(SegmentWriteState state) throws IOExcept
     public DocValuesProducer fieldsProducer(SegmentReadState state) throws IOException {
         return new ES819TSDBDocValuesProducer(state, DATA_CODEC, DATA_EXTENSION, META_CODEC, META_EXTENSION);
     }
+
+    public static ES819TSDBDocValuesFormat load(IndexVersion indexVersion) {
+        boolean enableOptimizedMerge = indexVersion.onOrAfter(IndexVersions.USE_819_TSDB_DOC_VALUES_FORMAT);
+        return new ES819TSDBDocValuesFormat(DEFAULT_SKIP_INDEX_INTERVAL_SIZE, enableOptimizedMerge);
+    }
 }