Merge branch 'main' into mtv2

Author: jdconrad

muted-tests.yml

@@ -537,9 +537,6 @@ tests:
 - class: org.elasticsearch.compute.data.BasicBlockTests
   method: testFloatBlock
   issue: https://github.com/elastic/elasticsearch/issues/133621
-- class: org.elasticsearch.xpack.esql.qa.mixed.MixedClusterEsqlSpecIT
-  method: test {csv-spec:inlinestats.EvalBeforeDoubleInlinestats1}
-  issue: https://github.com/elastic/elasticsearch/issues/133729
 - class: org.elasticsearch.xpack.esql.qa.single_node.GenerativeIT
   method: test
   issue: https://github.com/elastic/elasticsearch/issues/133077

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

@@ -15,6 +15,7 @@
 import org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
 import org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsFormat;
 import org.elasticsearch.common.util.BigArrays;
+import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.IndexVersions;
@@ -25,6 +26,7 @@
 import org.elasticsearch.index.mapper.IdFieldMapper;
 import org.elasticsearch.index.mapper.Mapper;
 import org.elasticsearch.index.mapper.MapperService;
+import org.elasticsearch.index.mapper.SeqNoFieldMapper;
 import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper;
 
 /**
@@ -33,6 +35,8 @@
  */
 public class PerFieldFormatSupplier {
 
+    private static final FeatureFlag SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT = new FeatureFlag("seqno_field_use_tsdb_doc_values_format");
+
     private static final DocValuesFormat docValuesFormat = new Lucene90DocValuesFormat();
     private static final KnnVectorsFormat knnVectorsFormat = new Lucene99HnswVectorsFormat();
     private static final ES819TSDBDocValuesFormat tsdbDocValuesFormat = new ES819TSDBDocValuesFormat();
@@ -122,9 +126,13 @@ boolean useTSDBDocValuesFormat(final String field) {
     }
 
     private boolean excludeFields(String fieldName) {
+        // TODO: should we just allow all fields to use tsdb doc values codec?
         // Avoid using tsdb codec for fields like _seq_no, _primary_term.
         // But _tsid and _ts_routing_hash should always use the tsdb codec.
-        return fieldName.startsWith("_") && fieldName.equals("_tsid") == false && fieldName.equals("_ts_routing_hash") == false;
+        return fieldName.startsWith("_")
+            && fieldName.equals("_tsid") == false
+            && fieldName.equals("_ts_routing_hash") == false
+            && (SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT.isEnabled() && fieldName.equals(SeqNoFieldMapper.NAME) == false);
     }
 
     private boolean isTimeSeriesModeIndex() {