Remove dead code from ShardSearchStats (elastic#37421)

The clear methodsa are unused and unsafe at this point. This commit
removes the dead code.

Author: s1monw

server/src/main/java/org/elasticsearch/index/search/stats/ShardSearchStats.java

@@ -122,27 +122,11 @@ public void onFetchPhase(SearchContext searchContext, long tookInNanos) {
         });
     }
 
-    public void clear() {
-        totalStats.clear();
-        synchronized (this) {
-            if (!groupsStats.isEmpty()) {
-                MapBuilder<String, StatsHolder> typesStatsBuilder = MapBuilder.newMapBuilder();
-                for (Map.Entry<String, StatsHolder> typeStats : groupsStats.entrySet()) {
-                    if (typeStats.getValue().totalCurrent() > 0) {
-                        typeStats.getValue().clear();
-                        typesStatsBuilder.put(typeStats.getKey(), typeStats.getValue());
-                    }
-                }
-                groupsStats = typesStatsBuilder.immutableMap();
-            }
-        }
-    }
-
     private void computeStats(SearchContext searchContext, Consumer<StatsHolder> consumer) {
         consumer.accept(totalStats);
         if (searchContext.groupStats() != null) {
-            for (int i = 0; i < searchContext.groupStats().size(); i++) {
-                consumer.accept(groupStats(searchContext.groupStats().get(i)));
+            for (String group : searchContext.groupStats()) {
+                consumer.accept(groupStats(group));
             }
         }
     }
@@ -184,40 +168,29 @@ public void onFreeScrollContext(SearchContext context) {
     }
 
     static final class StatsHolder {
-        public final MeanMetric queryMetric = new MeanMetric();
-        public final MeanMetric fetchMetric = new MeanMetric();
+        final MeanMetric queryMetric = new MeanMetric();
+        final MeanMetric fetchMetric = new MeanMetric();
         /* We store scroll statistics in microseconds because with nanoseconds we run the risk of overflowing the total stats if there are
          * many scrolls. For example, on a system with 2^24 scrolls that have been executed, each executing for 2^10 seconds, then using
          * nanoseconds would require a numeric representation that can represent at least 2^24 * 2^10 * 10^9 > 2^24 * 2^10 * 2^29 = 2^63
          * which exceeds the largest value that can be represented by a long. By using microseconds, we enable capturing one-thousand
          * times as many scrolls (i.e., billions of scrolls which at one per second would take 32 years to occur), or scrolls that execute
          * for one-thousand times as long (i.e., scrolls that execute for almost twelve days on average).
          */
-        public final MeanMetric scrollMetric = new MeanMetric();
-        public final MeanMetric suggestMetric = new MeanMetric();
-        public final CounterMetric queryCurrent = new CounterMetric();
-        public final CounterMetric fetchCurrent = new CounterMetric();
-        public final CounterMetric scrollCurrent = new CounterMetric();
-        public final CounterMetric suggestCurrent = new CounterMetric();
-
-        public SearchStats.Stats stats() {
+        final MeanMetric scrollMetric = new MeanMetric();
+        final MeanMetric suggestMetric = new MeanMetric();
+        final CounterMetric queryCurrent = new CounterMetric();
+        final CounterMetric fetchCurrent = new CounterMetric();
+        final CounterMetric scrollCurrent = new CounterMetric();
+        final CounterMetric suggestCurrent = new CounterMetric();
+
+        SearchStats.Stats stats() {
             return new SearchStats.Stats(
                     queryMetric.count(), TimeUnit.NANOSECONDS.toMillis(queryMetric.sum()), queryCurrent.count(),
                     fetchMetric.count(), TimeUnit.NANOSECONDS.toMillis(fetchMetric.sum()), fetchCurrent.count(),
                     scrollMetric.count(), TimeUnit.MICROSECONDS.toMillis(scrollMetric.sum()), scrollCurrent.count(),
                     suggestMetric.count(), TimeUnit.NANOSECONDS.toMillis(suggestMetric.sum()), suggestCurrent.count()
             );
         }
-
-        public long totalCurrent() {
-            return queryCurrent.count() + fetchCurrent.count() + scrollCurrent.count() + suggestCurrent.count();
-        }
-
-        public void clear() {
-            queryMetric.clear();
-            fetchMetric.clear();
-            scrollMetric.clear();
-            suggestMetric.clear();
-        }
     }
 }