Enabling sort optimization back for half_float with custom comparators

CHANGELOG.md

@@ -21,6 +21,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [AdmissionControl] Added changes for AdmissionControl Interceptor and AdmissionControlService for RateLimiting ([#9286](https://github.com/opensearch-project/OpenSearch/pull/9286))
 - GHA to verify checklist items completion in PR descriptions ([#10800](https://github.com/opensearch-project/OpenSearch/pull/10800))
 - [Remote cluster state] Restore cluster state version during remote state auto restore ([#10853](https://github.com/opensearch-project/OpenSearch/pull/10853))
+- Add back half_float BKD based sort query optimization ([#11024](https://github.com/opensearch-project/OpenSearch/pull/11024))
 
 ### Dependencies
 - Bump `log4j-core` from 2.18.0 to 2.19.0
@@ -141,4 +142,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Security
 
 [Unreleased 3.0]: https://github.com/opensearch-project/OpenSearch/compare/2.x...HEAD
-[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.12...2.x
+[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.12...2.x

rest-api-spec/src/main/resources/rest-api-spec/test/indices.sort/10_basic.yml

@@ -156,3 +156,23 @@
           query: {"range": { "rank": { "from": 0 } } }
           track_total_hits: false
           size: 3
+
+---
+"Index Sort half float":
+  - do:
+      catch: bad_request
+      indices.create:
+        index: test
+        body:
+          settings:
+            number_of_shards: 1
+            number_of_replicas: 0
+            index.sort.field: rank
+          mappings:
+            properties:
+              rank:
+                type: half_float
+
+  # This should failed with 400 as half_float is not supported for index sort
+  - match: { status: 400 }
+  - match: { error.type: illegal_argument_exception }

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

@@ -20,6 +20,7 @@
             properties:
               counter:
                 type: double
+
   - do:
       bulk:
         refresh: true
@@ -119,3 +120,87 @@
   - match: { status: 400 }
   - match: { error.type: search_phase_execution_exception }
   - match: { error.caused_by.reason: "Can't do sort across indices, as a field has [unsigned_long] type in one index, and different type in another index!" }
+
+---
+"search across indices with mixed long and double and float numeric types":
+  - skip:
+      version: " - 2.10.99"
+      reason: half float was broken before 2.11
+
+  - 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:
+      indices.create:
+        index: test_3
+        body:
+          mappings:
+            properties:
+              counter:
+                type: half_float
+
+  - 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
+          - index:
+              _index: test_3
+          - counter: 187.4
+          - index:
+              _index: test_3
+          - counter: 194.4
+
+  - do:
+      search:
+        index: test_*
+        rest_total_hits_as_int: true
+        body:
+          sort: [{ counter: desc }]
+  - match: { hits.total: 5 }
+  - length: { hits.hits: 5 }
+  - match: { hits.hits.0._index: test_2 }
+  - match: { hits.hits.0._source.counter: 1223372036854775800.23 }
+  - match: { hits.hits.0.sort.0: 1223372036854775800.23 }
+  - match: { hits.hits.1._index: test_1 }
+  - match: { hits.hits.1._source.counter: 223372036854775800 }
+  - match: { hits.hits.1.sort.0: 223372036854775800  }
+  - match: { hits.hits.2._index: test_3 }
+  - match: { hits.hits.2._source.counter: 194.4 }
+
+  - do:
+      search:
+        index: test_*
+        rest_total_hits_as_int: true
+        body:
+          sort: [{ counter: asc }]
+  - match: { hits.total: 5 }
+  - length: { hits.hits: 5 }
+  - match: { hits.hits.0._index: test_2 }
+  - match: { hits.hits.0._source.counter: 184.4 }
+  - match: { hits.hits.0.sort.0: 184.4 }
+  - match: { hits.hits.1._index: test_3 }
+  - match: { hits.hits.1._source.counter: 187.4 }