Remove some redundant ref-counting from SearchHits

Remove ref-counting that is obviously redundant because of clear
ownership transfers from `SearchHits`.

Author: original-brownbear

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

@@ -273,26 +273,28 @@ public static SearchResponseSections merge(
         if (reducedQueryPhase.isEmptyResult) {
             return SearchResponseSections.EMPTY_WITH_TOTAL_HITS;
         }
-        ScoreDoc[] sortedDocs = reducedQueryPhase.sortedTopDocs.scoreDocs;
         var fetchResults = fetchResultsArray.asList();
-        final SearchHits hits = getHits(reducedQueryPhase, ignoreFrom, fetchResultsArray);
+        SearchHits hits = getHits(reducedQueryPhase, ignoreFrom, fetchResultsArray);
         try {
             if (reducedQueryPhase.suggest != null && fetchResults.isEmpty() == false) {
-                mergeSuggest(reducedQueryPhase, fetchResultsArray, hits, sortedDocs);
+                mergeSuggest(reducedQueryPhase, fetchResultsArray, hits.getHits().length, reducedQueryPhase.sortedTopDocs.scoreDocs);
             }
-            return reducedQueryPhase.buildResponse(hits, fetchResults);
+            var res = reducedQueryPhase.buildResponse(hits, fetchResults);
+            hits = null;
+            return res;
         } finally {
-            hits.decRef();
+            if (hits != null) {
+                hits.decRef();
+            }
         }
     }
 
     private static void mergeSuggest(
         ReducedQueryPhase reducedQueryPhase,
         AtomicArray<? extends SearchPhaseResult> fetchResultsArray,
-        SearchHits hits,
+        int currentOffset,
         ScoreDoc[] sortedDocs
     ) {
-        int currentOffset = hits.getHits().length;
         for (CompletionSuggestion suggestion : reducedQueryPhase.suggest.filter(CompletionSuggestion.class)) {
             final List<CompletionSuggestion.Entry.Option> suggestionOptions = suggestion.getOptions();
             for (int scoreDocIndex = currentOffset; scoreDocIndex < currentOffset + suggestionOptions.size(); scoreDocIndex++) {

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

@@ -61,7 +61,6 @@ public SearchResponseSections(
         int numReducePhases
     ) {
         this.hits = hits;
-        hits.incRef();
         this.aggregations = aggregations;
         this.suggest = suggest;
         this.profileResults = profileResults;

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

@@ -252,6 +252,7 @@ public boolean decRef() {
     }
 
     private void deallocate() {
+        var hits = this.hits;
         for (int i = 0; i < hits.length; i++) {
             assert hits[i] != null;
             hits[i].decRef();

server/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java

@@ -84,12 +84,18 @@ public void execute(SearchContext context, int[] docIdsToLoad, RankDocShardInfo
         try {
             hits = buildSearchHits(context, docIdsToLoad, profiler, rankDocs);
         } finally {
-            // Always finish profiling
-            ProfileResult profileResult = profiler.finish();
-            // Only set the shardResults if building search hits was successful
-            if (hits != null) {
-                context.fetchResult().shardResult(hits, profileResult);
-                hits.decRef();
+            try {
+                // Always finish profiling
+                ProfileResult profileResult = profiler.finish();
+                // Only set the shardResults if building search hits was successful
+                if (hits != null) {
+                    context.fetchResult().shardResult(hits, profileResult);
+                    hits = null;
+                }
+            } finally {
+                if (hits != null) {
+                    hits.decRef();
+                }
             }
         }
     }

server/src/main/java/org/elasticsearch/search/fetch/FetchSearchResult.java

@@ -68,7 +68,6 @@ public void shardResult(SearchHits hits, ProfileResult profileResult) {
             existing.decRef();
         }
         this.hits = hits;
-        hits.mustIncRef();
         assert this.profileResult == null;
         this.profileResult = profileResult;
     }