LUCENE-8592: Fix index sorting corruption due to numeric overflow

The merge sort of sorted segments can produce an invalid
sort if the sort field is an Integer/Long that uses reverse order and contains values equal to
Integer/Long#MIN_VALUE. These values are always sorted first during a merge
(instead of last because of the reverse order) due to this bug.
Indices affected by the bug can be detected by running the CheckIndex command on a
distribution that contains the fix (7.6+).

Author: jimczi

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

@@ -34,6 +34,7 @@
 import org.elasticsearch.search.SearchShardTarget;
 import org.elasticsearch.search.internal.AliasFilter;
 import org.elasticsearch.search.internal.InternalSearchResponse;
+import org.elasticsearch.search.internal.SearchContext;
 import org.elasticsearch.search.internal.ShardSearchTransportRequest;
 import org.elasticsearch.transport.Transport;
 
@@ -113,7 +114,11 @@ public final void start() {
         if (getNumShards() == 0) {
             //no search shards to search on, bail with empty response
             //(it happens with search across _all with no indices around and consistent with broadcast operations)
-            listener.onResponse(new SearchResponse(InternalSearchResponse.empty(), null, 0, 0, 0, buildTookInMillis(),
+
+            boolean withTotalHits = request.source() != null ?
+                // total hits is null in the response if the tracking of total hits is disabled
+                request.source().trackTotalHitsUpTo() != SearchContext.TRACK_TOTAL_HITS_DISABLED : true;
+            listener.onResponse(new SearchResponse(InternalSearchResponse.empty(withTotalHits), null, 0, 0, 0, buildTookInMillis(),
                 ShardSearchFailure.EMPTY_ARRAY, clusters));
             return;
         }

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

@@ -42,10 +42,13 @@
 import static org.elasticsearch.common.xcontent.XContentParserUtils.ensureExpectedToken;
 
 public final class SearchHits implements Streamable, ToXContentFragment, Iterable<SearchHit> {
-
     public static SearchHits empty() {
+        return empty(true);
+    }
+
+    public static SearchHits empty(boolean withTotalHits) {
         // We shouldn't use static final instance, since that could directly be returned by native transport clients
-        return new SearchHits(EMPTY, new TotalHits(0, Relation.EQUAL_TO), 0);
+        return new SearchHits(EMPTY, withTotalHits ? new TotalHits(0, Relation.EQUAL_TO) : null, 0);
     }
 
     public static final SearchHit[] EMPTY = new SearchHit[0];

server/src/main/java/org/elasticsearch/search/internal/InternalSearchResponse.java

@@ -35,9 +35,12 @@
  * {@link SearchResponseSections} subclass that can be serialized over the wire.
  */
 public class InternalSearchResponse extends SearchResponseSections implements Writeable, ToXContentFragment {
-
     public static InternalSearchResponse empty() {
-        return new InternalSearchResponse(SearchHits.empty(), null, null, null, false, null, 1);
+        return empty(true);
+    }
+
+    public static InternalSearchResponse empty(boolean withTotalHits) {
+        return new InternalSearchResponse(SearchHits.empty(withTotalHits), null, null, null, false, null, 1);
     }
 
     public InternalSearchResponse(SearchHits hits, InternalAggregations aggregations, Suggest suggest,