[Backport 2.x] Remove query categorization from core

CHANGELOG.md

@@ -49,6 +49,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Deprecated
 
 ### Removed
+- Remove query categorization changes ([#14759](https://github.com/opensearch-project/OpenSearch/pull/14759))
 
 ### Fixed
 - Fix bug in SBP cancellation logic ([#13259](https://github.com/opensearch-project/OpenSearch/pull/13474))

server/src/main/java/org/opensearch/action/search/TransportSearchAction.java

@@ -143,13 +143,6 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
         Property.NodeScope
     );
 
-    public static final Setting<Boolean> SEARCH_QUERY_METRICS_ENABLED_SETTING = Setting.boolSetting(
-        "search.query.metrics.enabled",
-        false,
-        Setting.Property.NodeScope,
-        Setting.Property.Dynamic
-    );
-
     // cluster level setting for timeout based search cancellation. If search request level parameter is present then that will take
     // precedence over the cluster setting value
     public static final String SEARCH_CANCEL_AFTER_TIME_INTERVAL_SETTING_KEY = "search.cancel_after_time_interval";
@@ -182,11 +175,8 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
     private final SearchRequestOperationsCompositeListenerFactory searchRequestOperationsCompositeListenerFactory;
     private final Tracer tracer;
 
-    private volatile boolean searchQueryMetricsEnabled;
-
     private final MetricsRegistry metricsRegistry;
 
-    private SearchQueryCategorizer searchQueryCategorizer;
     private TaskResourceTrackingService taskResourceTrackingService;
 
     @Inject
@@ -222,21 +212,11 @@ public TransportSearchAction(
         this.namedWriteableRegistry = namedWriteableRegistry;
         this.searchPipelineService = searchPipelineService;
         this.metricsRegistry = metricsRegistry;
-        this.searchQueryMetricsEnabled = clusterService.getClusterSettings().get(SEARCH_QUERY_METRICS_ENABLED_SETTING);
         this.searchRequestOperationsCompositeListenerFactory = searchRequestOperationsCompositeListenerFactory;
-        clusterService.getClusterSettings()
-            .addSettingsUpdateConsumer(SEARCH_QUERY_METRICS_ENABLED_SETTING, this::setSearchQueryMetricsEnabled);
         this.tracer = tracer;
         this.taskResourceTrackingService = taskResourceTrackingService;
     }
 
-    private void setSearchQueryMetricsEnabled(boolean searchQueryMetricsEnabled) {
-        this.searchQueryMetricsEnabled = searchQueryMetricsEnabled;
-        if ((this.searchQueryMetricsEnabled == true) && this.searchQueryCategorizer == null) {
-            this.searchQueryCategorizer = new SearchQueryCategorizer(metricsRegistry);
-        }
-    }
-
     private Map<String, AliasFilter> buildPerIndexAliasFilter(
         SearchRequest request,
         ClusterState clusterState,
@@ -473,13 +453,6 @@ private void executeRequest(
             }
 
             ActionListener<SearchRequest> requestTransformListener = ActionListener.wrap(sr -> {
-                if (searchQueryMetricsEnabled) {
-                    try {
-                        searchQueryCategorizer.categorize(sr.source());
-                    } catch (Exception e) {
-                        logger.error("Error while trying to categorize the query.", e);
-                    }
-                }
 
                 ActionListener<SearchSourceBuilder> rewriteListener = buildRewriteListener(
                     sr,

server/src/main/java/org/opensearch/common/settings/ClusterSettings.java

@@ -404,7 +404,6 @@ public void apply(Settings value, Settings current, Settings previous) {
                 SearchService.DEFAULT_ALLOW_PARTIAL_SEARCH_RESULTS,
                 TransportSearchAction.SHARD_COUNT_LIMIT_SETTING,
                 TransportSearchAction.SEARCH_CANCEL_AFTER_TIME_INTERVAL_SETTING,
-                TransportSearchAction.SEARCH_QUERY_METRICS_ENABLED_SETTING,
                 TransportSearchAction.SEARCH_PHASE_TOOK_ENABLED,
                 SearchRequestStats.SEARCH_REQUEST_STATS_ENABLED,
                 RemoteClusterService.REMOTE_CLUSTER_SKIP_UNAVAILABLE,