Use object equality to compare versions in IndexSettings (#18103)

Fixes an issue where updating index metadata on a index from a version that it does not have in its static list of known versions fails.

core/src/main/java/org/elasticsearch/index/IndexSettings.java

@@ -382,7 +382,7 @@ public final class IndexSettings {
      */
     synchronized boolean updateIndexMetaData(IndexMetaData indexMetaData) {
         final Settings newSettings = indexMetaData.getSettings();
-        if (Version.indexCreated(newSettings) != version) {
+        if (version.equals(Version.indexCreated(newSettings)) == false) {
             throw new IllegalArgumentException("version mismatch on settings update expected: " + version + " but was: " + Version.indexCreated(newSettings));
         }
         final String newUUID = newSettings.get(IndexMetaData.SETTING_INDEX_UUID, IndexMetaData.INDEX_UUID_NA_VALUE);

core/src/test/java/org/elasticsearch/index/IndexSettingsTests.java

@@ -110,6 +110,15 @@ public class IndexSettingsTests extends ESTestCase {
             assertTrue(ex.getMessage(), ex.getMessage().startsWith("version mismatch on settings update expected: "));
         }
 
+        // use version number that is unknown
+        metaData = newIndexMeta("index", Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.fromId(999999))
+            .build());
+        settings = new IndexSettings(metaData, Settings.EMPTY);
+        assertEquals(Version.fromId(999999), settings.getIndexVersionCreated());
+        assertEquals("_na_", settings.getUUID());
+        settings.updateIndexMetaData(newIndexMeta("index", Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED,
+            Version.fromId(999999)).put("index.test.setting.int", 42).build()));
+
         metaData = newIndexMeta("index", Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
             .put(IndexMetaData.SETTING_INDEX_UUID, "0xdeadbeef").build());
         settings = new IndexSettings(metaData, Settings.EMPTY);