Fixing SortField comparison to use equals instead of reference equality

Signed-off-by: Andriy Redko <andriy.redko@aiven.io>

rest-api-spec/src/main/resources/rest-api-spec/test/search/260_sort_mixed.yml

@@ -0,0 +1,65 @@
+"search across indices with mixed long and double numeric types":
+  - skip:
+      version: " - 2.6.99"
+      reason: relies on numeric sort optimization that landed in 2.7.0 only
+
+  - do:
+      indices.create:
+        index: test_1
+        body:
+          mappings:
+            properties:
+              counter:
+                type: long
+
+  - do:
+      indices.create:
+        index: test_2
+        body:
+          mappings:
+            properties:
+              counter:
+                type: double
+  - do:
+      bulk:
+        refresh: true
+        body:
+          - index:
+              _index: test_1
+          - counter: 223372036854775800
+          - index:
+              _index: test_2
+          - counter: 1223372036854775800.23
+          - index:
+              _index: test_2
+          - counter: 184.4
+
+  - do:
+      search:
+        index: test_*
+        rest_total_hits_as_int: true
+        body:
+          sort: [{ counter: desc }]
+  - match: { hits.total: 3 }
+  - length: { hits.hits: 3 }
+  - match: { hits.hits.0._index: test_2 }
+  - match: { hits.hits.0._source.counter: 1223372036854775800.23 }
+  - match: { hits.hits.0.sort: [1223372036854775800.23] }
+  - match: { hits.hits.1._index: test_1 }
+  - match: { hits.hits.1._source.counter: 223372036854775800 }
+  - match: { hits.hits.1.sort: [223372036854775800] }
+
+  - do:
+      search:
+        index: test_*
+        rest_total_hits_as_int: true
+        body:
+          sort: [{ counter: asc }]
+  - match: { hits.total: 3 }
+  - length: { hits.hits: 3 }
+  - match: { hits.hits.0._index: test_2 }
+  - match: { hits.hits.0._source.counter: 184.4 }
+  - match: { hits.hits.0.sort: [184.4] }
+  - match: { hits.hits.1._index: test_1 }
+  - match: { hits.hits.1._source.counter: 223372036854775800 }
+  - match: { hits.hits.1.sort: [223372036854775800] }

server/src/main/java/org/opensearch/action/search/SearchPhaseController.java

@@ -636,7 +636,7 @@ private static Sort createSort(TopFieldDocs[] topFieldDocs) {
      */
     private static boolean isSortWideningRequired(TopFieldDocs[] topFieldDocs, int sortFieldindex) {
         for (int i = 0; i < topFieldDocs.length - 1; i++) {
-            if (topFieldDocs[i].fields[sortFieldindex] != topFieldDocs[i + 1].fields[sortFieldindex]) {
+            if (!topFieldDocs[i].fields[sortFieldindex].equals(topFieldDocs[i + 1].fields[sortFieldindex])) {
                 return true;
             }
         }