Add search.default_exclude_vectors setting as fallback

Author: Rassyan

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

@@ -126,6 +126,7 @@
 import org.elasticsearch.search.SearchService;
 import org.elasticsearch.search.aggregations.MultiBucketConsumerService;
 import org.elasticsearch.search.aggregations.metrics.TDigestExecutionHint;
+import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import org.elasticsearch.search.fetch.subphase.highlight.FastVectorHighlighter;
 import org.elasticsearch.snapshots.InternalSnapshotsInfoService;
 import org.elasticsearch.snapshots.RestoreService;
@@ -547,6 +548,7 @@ public void apply(Settings value, Settings current, Settings previous) {
         ThreadPool.SLOW_SCHEDULER_TASK_WARN_THRESHOLD_SETTING,
         ThreadPool.WRITE_THREAD_POOLS_EWMA_ALPHA_SETTING,
         FastVectorHighlighter.SETTING_TV_HIGHLIGHT_MULTI_VALUE,
+        FetchSourceContext.DEFAULT_SOURCE_EXCLUDE_VECTORS,
         Node.BREAKER_TYPE_KEY,
         OperationRouting.USE_ADAPTIVE_REPLICA_SELECTION_SETTING,
         IndexGraveyard.SETTING_MAX_TOMBSTONES,

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

@@ -102,6 +102,7 @@
 import org.elasticsearch.search.fetch.ShardFetchRequest;
 import org.elasticsearch.search.fetch.subphase.FetchDocValuesContext;
 import org.elasticsearch.search.fetch.subphase.FetchFieldsContext;
+import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import org.elasticsearch.search.fetch.subphase.ScriptFieldsContext.ScriptField;
 import org.elasticsearch.search.fetch.subphase.highlight.HighlightBuilder;
 import org.elasticsearch.search.internal.AliasFilter;
@@ -445,6 +446,9 @@ public SearchService(
         clusterService.getClusterSettings()
             .addSettingsUpdateConsumer(MEMORY_ACCOUNTING_BUFFER_SIZE, newValue -> this.memoryAccountingBufferSize = newValue.getBytes());
         prewarmingMaxPoolFactorThreshold = PREWARMING_THRESHOLD_THREADPOOL_SIZE_FACTOR_POOL_SIZE.get(settings);
+
+        clusterService.getClusterSettings()
+            .initializeAndWatch(FetchSourceContext.DEFAULT_SOURCE_EXCLUDE_VECTORS, FetchSourceContext::setDefaultSourceExcludeVectors);
     }
 
     public CircuitBreaker getCircuitBreaker() {

server/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceContext.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.rest.RestRequest;
@@ -40,6 +41,14 @@ public class FetchSourceContext implements Writeable, ToXContentObject {
     public static final ParseField INCLUDES_FIELD = new ParseField("includes", "include");
     public static final ParseField EXCLUDES_FIELD = new ParseField("excludes", "exclude");
 
+    public static final Setting<Boolean> DEFAULT_SOURCE_EXCLUDE_VECTORS = Setting.boolSetting(
+        "search.default_exclude_vectors",
+        true,
+        Setting.Property.NodeScope,
+        Setting.Property.Dynamic
+    );
+    private static volatile Boolean defaultSourceExcludeVectors;
+
     public static final FetchSourceContext FETCH_SOURCE = new FetchSourceContext(true, null, Strings.EMPTY_ARRAY, Strings.EMPTY_ARRAY);
     public static final FetchSourceContext FETCH_ALL_SOURCE = new FetchSourceContext(true, false, Strings.EMPTY_ARRAY, Strings.EMPTY_ARRAY);
 
@@ -89,6 +98,14 @@ public static FetchSourceContext readFrom(StreamInput in) throws IOException {
         return of(fetchSource, excludeVectors, includes, excludes);
     }
 
+    public static void setDefaultSourceExcludeVectors(boolean defaultSourceExcludeVectors) {
+        if (defaultSourceExcludeVectors) {
+            FetchSourceContext.defaultSourceExcludeVectors = null;
+        } else {
+            FetchSourceContext.defaultSourceExcludeVectors = false;
+        }
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeBoolean(fetchSource);
@@ -157,7 +174,7 @@ public static FetchSourceContext parseFromRestRequest(RestRequest request) {
             sourceExcludes = Strings.splitStringByCommaToArray(sExcludes);
         }
 
-        Boolean excludeVectors = request.paramAsBoolean("_source_exclude_vectors", null);
+        Boolean excludeVectors = request.paramAsBoolean("_source_exclude_vectors", defaultSourceExcludeVectors);
 
         if (excludeVectors != null || fetchSource != null || sourceIncludes != null || sourceExcludes != null) {
             return FetchSourceContext.of(fetchSource == null || fetchSource, excludeVectors, sourceIncludes, sourceExcludes);