Removed seqno_field_use_tsdb_doc_values_format feature flag (elastic#135374)

Author: Kubik42

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

@@ -15,7 +15,6 @@
 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;
@@ -41,7 +40,6 @@
  */
 public class PerFieldFormatSupplier {
 
-    static final FeatureFlag SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT = new FeatureFlag("seqno_field_use_tsdb_doc_values_format");
     private static final Set<String> INCLUDE_META_FIELDS;
 
     static {
@@ -51,9 +49,7 @@ public class PerFieldFormatSupplier {
         Set<String> includeMetaField = new HashSet<>(3);
         includeMetaField.add(TimeSeriesIdFieldMapper.NAME);
         includeMetaField.add(TimeSeriesRoutingHashFieldMapper.NAME);
-        if (SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT.isEnabled()) {
-            includeMetaField.add(SeqNoFieldMapper.NAME);
-        }
+        includeMetaField.add(SeqNoFieldMapper.NAME);
         // Don't the include _recovery_source_size and _recovery_source fields, since their values can be trimmed away in
         // RecoverySourcePruneMergePolicy, which leads to inconsistencies between merge stats and actual values.
         INCLUDE_META_FIELDS = Collections.unmodifiableSet(includeMetaField);

server/src/test/java/org/elasticsearch/index/codec/PerFieldMapperCodecTests.java

@@ -215,23 +215,10 @@ public void testMetaFields() throws IOException {
     }
 
     public void testSeqnoField() throws IOException {
-        assumeTrue(
-            "seqno_field_use_tsdb_doc_values_format should be enabled",
-            PerFieldFormatSupplier.SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT.isEnabled()
-        );
         PerFieldFormatSupplier perFieldMapperCodec = createFormatSupplier(true, IndexMode.LOGSDB, MAPPING_3);
         assertThat((perFieldMapperCodec.useTSDBDocValuesFormat(SeqNoFieldMapper.NAME)), is(true));
     }
 
-    public void testSeqnoFieldFeatureFlagDisabled() throws IOException {
-        assumeTrue(
-            "seqno_field_use_tsdb_doc_values_format should be disabled",
-            PerFieldFormatSupplier.SEQNO_FIELD_USE_TSDB_DOC_VALUES_FORMAT.isEnabled() == false
-        );
-        PerFieldFormatSupplier perFieldMapperCodec = createFormatSupplier(true, IndexMode.LOGSDB, MAPPING_3);
-        assertThat((perFieldMapperCodec.useTSDBDocValuesFormat(SeqNoFieldMapper.NAME)), is(false));
-    }
-
     private PerFieldFormatSupplier createFormatSupplier(boolean enableES87TSDBCodec, IndexMode mode, String mapping) throws IOException {
         Settings.Builder settings = Settings.builder();
         settings.put(IndexSettings.MODE.getKey(), mode);