Add IndexVersion in preparation to backport default BBQ (#127756)

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

@@ -140,6 +140,7 @@ public class IndexVersions {
     public static final IndexVersion ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS_BACKPORT_8_X = def(8_528_0_00, Version.LUCENE_9_12_1);
     public static final IndexVersion RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS_BACKPORT_8_X = def(8_529_0_00, Version.LUCENE_9_12_1);
     public static final IndexVersion DEFAULT_OVERSAMPLE_VALUE_FOR_BBQ_BACKPORT_8_X = def(8_530_0_00, Version.LUCENE_9_12_1);
+    public static final IndexVersion SEMANTIC_TEXT_DEFAULTS_TO_BBQ_BACKPORT_8_X = def(8_531_0_00, Version.LUCENE_9_12_1);
     public static final IndexVersion UPGRADE_TO_LUCENE_10_0_0 = def(9_000_0_00, Version.LUCENE_10_0_0);
     public static final IndexVersion LOGSDB_DEFAULT_IGNORE_DYNAMIC_BEYOND_LIMIT = def(9_001_0_00, Version.LUCENE_10_0_0);
     public static final IndexVersion TIME_BASED_K_ORDERED_DOC_ID = def(9_002_0_00, Version.LUCENE_10_0_0);

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapper.java

@@ -32,6 +32,7 @@ import org.elasticsearch.core.Nullable;
 import org.elasticsearch.features.NodeFeature;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.IndexVersion;
+import org.elasticsearch.index.IndexVersions;
 import org.elasticsearch.index.fielddata.FieldDataContext;
 import org.elasticsearch.index.fielddata.IndexFieldData;
 import org.elasticsearch.index.mapper.BlockLoader;
@@ -98,6 +99,7 @@ import java.util.function.Function;
 import java.util.function.Supplier;
 
 import static org.elasticsearch.index.IndexVersions.SEMANTIC_TEXT_DEFAULTS_TO_BBQ;
+import static org.elasticsearch.index.IndexVersions.SEMANTIC_TEXT_DEFAULTS_TO_BBQ_BACKPORT_8_X;
 import static org.elasticsearch.inference.TaskType.SPARSE_EMBEDDING;
 import static org.elasticsearch.inference.TaskType.TEXT_EMBEDDING;
 import static org.elasticsearch.search.SearchService.DEFAULT_SIZE;
@@ -1077,7 +1079,8 @@ public class SemanticTextFieldMapper extends FieldMapper implements InferenceFie
                 denseVectorMapperBuilder.elementType(modelSettings.elementType());
 
                 DenseVectorFieldMapper.IndexOptions defaultIndexOptions = null;
-                if (indexVersionCreated.onOrAfter(SEMANTIC_TEXT_DEFAULTS_TO_BBQ)) {
+                if (indexVersionCreated.onOrAfter(SEMANTIC_TEXT_DEFAULTS_TO_BBQ)
+                    || indexVersionCreated.between(SEMANTIC_TEXT_DEFAULTS_TO_BBQ_BACKPORT_8_X, IndexVersions.UPGRADE_TO_LUCENE_10_0_0)) {
                     defaultIndexOptions = defaultSemanticDenseIndexOptions();
                 }
                 if (defaultIndexOptions != null