Skip can_match phase with batched execution

If batched query execution is used, anything past the coordinator
rewrite phase is somewhat pointless. Just sort the shards in natural
order and be done with it as if there was no can_match.

Author: original-brownbear

server/src/main/java/org/elasticsearch/action/search/CanMatchPreFilterSearchPhase.java

@@ -167,9 +167,14 @@ private void runCoordinatorRewritePhase() {
         if (matchedShardLevelRequests.isEmpty()) {
             finishPhase();
         } else {
-            // verify missing shards only for the shards that we hit for the query
-            checkNoMissingShards(matchedShardLevelRequests);
-            new Round(matchedShardLevelRequests).run();
+            if (SearchService.BATCHED_QUERY_PHASE_FEATURE_FLAG) {
+                matchedShardLevelRequests.sort(SearchShardIterator::compareTo);
+                listener.onResponse(matchedShardLevelRequests);
+            } else {
+                // verify missing shards only for the shards that we hit for the query
+                checkNoMissingShards(matchedShardLevelRequests);
+                new Round(matchedShardLevelRequests).run();
+            }
         }
     }
 

server/src/main/java/org/elasticsearch/search/SearchService.java

@@ -282,7 +282,7 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
         Property.NodeScope
     );
 
-    private static final boolean BATCHED_QUERY_PHASE_FEATURE_FLAG = new FeatureFlag("batched_query_phase").isEnabled();
+    public static final boolean BATCHED_QUERY_PHASE_FEATURE_FLAG = new FeatureFlag("batched_query_phase").isEnabled();
 
     /**
      * The size of the buffer used for memory accounting.