Fix RemoteVersion comparison to prioritize OpenSearch over Elasticsearch

Signed-off-by: Hyunsang Han <[email protected]>

Author: HyunSangHan

modules/reindex/src/main/java/org/opensearch/index/reindex/remote/RemoteVersion.java

@@ -96,6 +96,10 @@ public int compareTo(RemoteVersion other) {
             return 1;
         }
 
+        if (this.isOpenSearch != other.isOpenSearch) {
+            return this.isOpenSearch ? 1 : -1;
+        }
+
         int result = Integer.compare(this.major, other.major);
         if (result != 0) {
             return result;

modules/reindex/src/test/java/org/opensearch/index/reindex/remote/RemoteVersionTests.java

@@ -36,9 +36,11 @@ public void testVersionComparison() {
         // Test compareTo()
         assertTrue(RemoteVersion.ELASTICSEARCH_1_0_0.compareTo(RemoteVersion.ELASTICSEARCH_2_0_0) < 0);
         assertTrue(RemoteVersion.ELASTICSEARCH_2_0_0.compareTo(RemoteVersion.ELASTICSEARCH_1_0_0) > 0);
+        assertTrue(RemoteVersion.ELASTICSEARCH_2_0_0.compareTo(RemoteVersion.ELASTICSEARCH_2_0_0) == 0);
 
         // Test OpenSearch vs Elasticsearch versions with same numbers
-        assertEquals(0, RemoteVersion.ELASTICSEARCH_2_0_0.compareTo(RemoteVersion.OPENSEARCH_2_0_0));
+        assertTrue(RemoteVersion.ELASTICSEARCH_2_0_0.compareTo(RemoteVersion.OPENSEARCH_2_0_0) < 0);
+        assertTrue(RemoteVersion.OPENSEARCH_2_0_0.compareTo(RemoteVersion.ELASTICSEARCH_2_0_0) > 0);
     }
 
     public void testVersionFromString() {