Fix bitset filter cache loading in Stateless (elastic#114191)

As recognized in PR elastic#113478 reviewing, the bitset filter cache
was wrongly eagerly loaded only for fast refresh indices on index
nodes. However, it should be eagerly loaded for any index that
can be searched. This PR fixes this.

Author: kingherc

server/src/main/java/org/elasticsearch/index/cache/bitset/BitsetFilterCache.java

@@ -58,8 +58,6 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 
-import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
-
 /**
  * This is a cache for {@link BitDocIdSet} based filters and is unbounded by size or time.
  * <p>
@@ -105,9 +103,7 @@ static boolean shouldLoadRandomAccessFiltersEagerly(IndexSettings settings) {
         boolean loadFiltersEagerlySetting = settings.getValue(INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING);
         boolean isStateless = DiscoveryNode.isStateless(settings.getNodeSettings());
         if (isStateless) {
-            return DiscoveryNode.hasRole(settings.getNodeSettings(), DiscoveryNodeRole.SEARCH_ROLE)
-                && loadFiltersEagerlySetting
-                && INDEX_FAST_REFRESH_SETTING.get(settings.getSettings());
+            return loadFiltersEagerlySetting && DiscoveryNode.hasRole(settings.getNodeSettings(), DiscoveryNodeRole.SEARCH_ROLE);
         } else {
             return loadFiltersEagerlySetting;
         }

server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java

@@ -48,7 +48,6 @@
 import java.util.concurrent.atomic.AtomicLong;
 
 import static org.elasticsearch.cluster.node.DiscoveryNode.STATELESS_ENABLED_SETTING_NAME;
-import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
 import static org.elasticsearch.index.cache.bitset.BitsetFilterCache.INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -271,38 +270,23 @@ public void onRemoval(ShardId shardId, Accountable accountable) {
     public void testShouldLoadRandomAccessFiltersEagerly() {
         var values = List.of(true, false);
         for (var hasIndexRole : values) {
-            for (var indexFastRefresh : values) {
-                for (var loadFiltersEagerly : values) {
-                    for (var isStateless : values) {
-                        if (isStateless) {
-                            assertEquals(
-                                loadFiltersEagerly && indexFastRefresh && hasIndexRole == false,
-                                BitsetFilterCache.shouldLoadRandomAccessFiltersEagerly(
-                                    bitsetFilterCacheSettings(isStateless, hasIndexRole, loadFiltersEagerly, indexFastRefresh)
-                                )
-                            );
-                        } else {
-                            assertEquals(
-                                loadFiltersEagerly,
-                                BitsetFilterCache.shouldLoadRandomAccessFiltersEagerly(
-                                    bitsetFilterCacheSettings(isStateless, hasIndexRole, loadFiltersEagerly, indexFastRefresh)
-                                )
-                            );
-                        }
+            for (var loadFiltersEagerly : values) {
+                for (var isStateless : values) {
+                    boolean result = BitsetFilterCache.shouldLoadRandomAccessFiltersEagerly(
+                        bitsetFilterCacheSettings(isStateless, hasIndexRole, loadFiltersEagerly)
+                    );
+                    if (isStateless) {
+                        assertEquals(loadFiltersEagerly && hasIndexRole == false, result);
+                    } else {
+                        assertEquals(loadFiltersEagerly, result);
                     }
                 }
             }
         }
     }
 
-    private IndexSettings bitsetFilterCacheSettings(
-        boolean isStateless,
-        boolean hasIndexRole,
-        boolean loadFiltersEagerly,
-        boolean indexFastRefresh
-    ) {
+    private IndexSettings bitsetFilterCacheSettings(boolean isStateless, boolean hasIndexRole, boolean loadFiltersEagerly) {
         var indexSettingsBuilder = Settings.builder().put(INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING.getKey(), loadFiltersEagerly);
-        if (isStateless) indexSettingsBuilder.put(INDEX_FAST_REFRESH_SETTING.getKey(), indexFastRefresh);
 
         var nodeSettingsBuilder = Settings.builder()
             .putList(