Fix bug in single shard optimization when sorting documents in search request

This commit adds a function to shard-level query result to determine whether
there are any hits that needs fetching. Currently, a shard-level query result
can have hits when there are search hits and/or completion suggestion hits.
The newly added function encapsulates the checks to determine if a shard-level
query result has any fetchable hits, which is used in optimizing for sorting
documents and releasing search request contexts.

core/src/main/java/org/elasticsearch/action/search/AbstractSearchAsyncAction.java

@@ -322,11 +322,8 @@ abstract class AbstractSearchAsyncAction<FirstResult extends SearchPhaseResult>
         // we only release search context that we did not fetch from if we are not scrolling
         if (request.scroll() == null) {
             for (AtomicArray.Entry<? extends QuerySearchResultProvider> entry : queryResults.asList()) {
-                QuerySearchResult queryResult = entry.value.queryResult().queryResult();
-                final TopDocs topDocs = queryResult.topDocs();
-                final Suggest suggest = queryResult.suggest();
-                if (((topDocs != null && topDocs.scoreDocs.length > 0) // the shard had matches
-                    ||suggest != null && suggest.hasScoreDocs()) // or had suggest docs
+                QuerySearchResult queryResult = entry.value.queryResult();
+                if (queryResult.hasHits()
                     && docIdsToLoad.get(entry.index) == null) { // but none of them made it to the global top docs
                     try {
                         DiscoveryNode node = nodes.get(entry.value.queryResult().shardTarget().nodeId());

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

@@ -269,7 +269,7 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
 
             loadOrExecuteQueryPhase(request, context);
 
-            if (hasHits(context.queryResult()) == false && context.scrollContext() == null) {
+            if (context.queryResult().hasHits() == false && context.scrollContext() == null) {
                 freeContext(context.id());
             } else {
                 contextProcessedSuccessfully(context);
@@ -324,7 +324,7 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
             operationListener.onPreQueryPhase(context);
             long time = System.nanoTime();
             queryPhase.execute(context);
-            if (hasHits(context.queryResult()) == false && context.scrollContext() == null) {
+            if (context.queryResult().hasHits() == false && context.scrollContext() == null) {
                 // no hits, we can release the context since there will be no fetch phase
                 freeContext(context.id());
             } else {
@@ -861,11 +861,6 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
         context.docIdsToLoad(docIdsToLoad, 0, docIdsToLoad.length);
     }
 
-    private static boolean hasHits(final QuerySearchResult searchResult) {
-        return searchResult.topDocs().scoreDocs.length > 0 ||
-            (searchResult.suggest() != null && searchResult.suggest().hasScoreDocs());
-    }
-
     private void processScroll(InternalScrollSearchRequest request, SearchContext context) {
         // process scroll
         context.from(context.from() + context.size());

core/src/main/java/org/elasticsearch/search/controller/SearchPhaseController.java

@@ -181,7 +181,7 @@ public class SearchPhaseController extends AbstractComponent {
         } else {
             // lets see if we only got hits from a single shard, if so, we can optimize...
             for (AtomicArray.Entry<? extends QuerySearchResultProvider> entry : results) {
-                if (entry.value.queryResult().topDocs().scoreDocs.length > 0) {
+                if (entry.value.queryResult().hasHits()) {
                     if (result != null) { // we already have one, can't really optimize
                         canOptimize = false;
                         break;

core/src/main/java/org/elasticsearch/search/query/QuerySearchResult.java

@@ -188,6 +188,12 @@ public class QuerySearchResult extends QuerySearchResultProvider {
         return this;
     }
 
+    /** Returns true iff the result has hits */
+    public boolean hasHits() {
+        return (topDocs != null && topDocs.scoreDocs.length > 0) ||
+            (suggest != null && suggest.hasScoreDocs());
+    }
+
     public static QuerySearchResult readQuerySearchResult(StreamInput in) throws IOException {
         QuerySearchResult result = new QuerySearchResult();
         result.readFrom(in);