add index version check

Author: martijnvg

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

@@ -147,6 +147,7 @@ private static Version parseUnchecked(String version) {
     public static final IndexVersion UPGRADE_TO_LUCENE_10_1_0 = def(9_009_0_00, Version.LUCENE_10_1_0);
     public static final IndexVersion USE_SYNTHETIC_SOURCE_FOR_RECOVERY_BY_DEFAULT = def(9_010_00_0, Version.LUCENE_10_1_0);
     public static final IndexVersion TIMESTAMP_DOC_VALUES_SPARSE_INDEX = def(9_011_0_00, Version.LUCENE_10_1_0);
+    public static final IndexVersion SYNTHETIC_SOURCE_STORE_ARRAYS_NATIVELY_KEYWORD = def(9_012_0_00, Version.LUCENE_10_1_0);
     /*
      * STOP! READ THIS FIRST! No, really,
      *        ____ _____ ___  ____  _        ____  _____    _    ____    _____ _   _ ___ ____    _____ ___ ____  ____ _____ _

server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java

@@ -446,7 +446,8 @@ public KeywordFieldMapper build(MapperBuilderContext context) {
                 && hasDocValues()
                 && fieldtype.stored() == false
                 && copyTo.copyToFields().isEmpty()
-                && multiFieldsBuilder.hasMultiFields() == false) {
+                && multiFieldsBuilder.hasMultiFields() == false
+                && indexCreatedVersion.onOrAfter(IndexVersions.SYNTHETIC_SOURCE_STORE_ARRAYS_NATIVELY_KEYWORD)) {
                 // Skip stored, we will be synthesizing from stored fields, no point to keep track of the offsets
                 // Skip copy_to and multi fields, supporting that requires more work. However, copy_to usage is rare in metrics and
                 // logging use cases