Don't mark shard as refreshPending on stats fetching (#40458)

Completion and DocStats are pulled from internal readers
instead of external since #33835 and #33847 which doesn't require
us to refresh after a stats call since refreshes will happen internally
anyhow and that will cause updated stats on ongoing indexing.

Author: s1monw

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -947,9 +947,7 @@ public FlushStats flushStats() {
 
     public DocsStats docStats() {
         readAllowed();
-        DocsStats docsStats = getEngine().docStats();
-        markSearcherAccessed();
-        return docsStats;
+        return getEngine().docStats();
     }
 
     /**
@@ -1028,11 +1026,7 @@ public TranslogStats translogStats() {
     public CompletionStats completionStats(String... fields) {
         readAllowed();
         try {
-            CompletionStats stats = getEngine().completionStats(fields);
-            // we don't wait for a pending refreshes here since it's a stats call instead we mark it as accessed only which will cause
-            // the next scheduled refresh to go through and refresh the stats as well
-            markSearcherAccessed();
-            return stats;
+            return getEngine().completionStats(fields);
         } catch (IOException e) {
             throw new UncheckedIOException(e);
         }

server/src/test/java/org/elasticsearch/index/shard/IndexShardTests.java

@@ -2767,7 +2767,7 @@ public void testCompletionStatsMarksSearcherAccessed() throws Exception {
             });
             long prevAccessTime = shard.getLastSearcherAccess();
             indexShard.completionStats();
-            assertThat("searcher was not marked as accessed", shard.getLastSearcherAccess(), greaterThan(prevAccessTime));
+            assertThat("searcher was marked as accessed", shard.getLastSearcherAccess(), equalTo(prevAccessTime));
         } finally {
             closeShards(indexShard);
         }
@@ -2797,7 +2797,7 @@ public void testDocStats() throws Exception {
                 });
                 long prevAccessTime = shard.getLastSearcherAccess();
                 final DocsStats docsStats = indexShard.docStats();
-                assertThat("searcher was not marked as accessed", shard.getLastSearcherAccess(), greaterThan(prevAccessTime));
+                assertThat("searcher was marked as accessed", shard.getLastSearcherAccess(), equalTo(prevAccessTime));
                 assertThat(docsStats.getCount(), equalTo(numDocs));
                 try (Engine.Searcher searcher = indexShard.acquireSearcher("test")) {
                     assertTrue(searcher.reader().numDocs() <= docsStats.getCount());