diff --git a/src/main/java/it/cavallium/dbengine/database/LLItem.java b/src/main/java/it/cavallium/dbengine/database/LLItem.java
index ae57de0..45988fa 100644
--- a/src/main/java/it/cavallium/dbengine/database/LLItem.java
+++ b/src/main/java/it/cavallium/dbengine/database/LLItem.java
@@ -81,6 +81,10 @@ public class LLItem {
 		return new LLItem(LLType.SortedNumericDocValuesField, name, data);
 	}
 
+	public static LLItem newNumericDocValuesField(String name, long data) {
+		return new LLItem(LLType.NumericDocValuesField, name, data);
+	}
+
 	public String getName() {
 		return name;
 	}
diff --git a/src/main/java/it/cavallium/dbengine/database/LLType.java b/src/main/java/it/cavallium/dbengine/database/LLType.java
index 2e174b1..54a1b3a 100644
--- a/src/main/java/it/cavallium/dbengine/database/LLType.java
+++ b/src/main/java/it/cavallium/dbengine/database/LLType.java
@@ -1,5 +1,8 @@
 package it.cavallium.dbengine.database;
 
+/**
+ * https://lucene.apache.org/core/8_0_0/core/org/apache/lucene/document/Field.html
+ */
 public enum LLType {
 	StringField,
 	StringFieldStored,
@@ -7,6 +10,7 @@ public enum LLType {
 	LongPoint,
 	LongStoredField,
 	FloatPoint,
+	NumericDocValuesField,
 	SortedNumericDocValuesField,
 	TextField,
 	TextFieldStored
diff --git a/src/main/java/it/cavallium/dbengine/database/LLUtils.java b/src/main/java/it/cavallium/dbengine/database/LLUtils.java
index 9bab5cf..9140397 100644
--- a/src/main/java/it/cavallium/dbengine/database/LLUtils.java
+++ b/src/main/java/it/cavallium/dbengine/database/LLUtils.java
@@ -34,6 +34,7 @@ import org.apache.lucene.document.Field;
 import org.apache.lucene.document.FloatPoint;
 import org.apache.lucene.document.IntPoint;
 import org.apache.lucene.document.LongPoint;
+import org.apache.lucene.document.NumericDocValuesField;
 import org.apache.lucene.document.SortedNumericDocValuesField;
 import org.apache.lucene.document.StoredField;
 import org.apache.lucene.document.StringField;
@@ -179,9 +180,9 @@ public class LLUtils {
 			case FloatPoint -> new FloatPoint(item.getName(), ByteBuffer.wrap(item.getData()).getFloat());
 			case TextField -> new TextField(item.getName(), item.stringValue(), Field.Store.NO);
 			case TextFieldStored -> new TextField(item.getName(), item.stringValue(), Field.Store.YES);
-			case SortedNumericDocValuesField -> new SortedNumericDocValuesField(item.getName(),
-					Longs.fromByteArray(item.getData())
-			);
+			case SortedNumericDocValuesField ->
+					new SortedNumericDocValuesField(item.getName(), Longs.fromByteArray(item.getData()));
+			case NumericDocValuesField -> new NumericDocValuesField(item.getName(), Longs.fromByteArray(item.getData()));
 			case StringField -> new StringField(item.getName(), item.stringValue(), Field.Store.NO);
 			case StringFieldStored -> new StringField(item.getName(), item.stringValue(), Field.Store.YES);
 		};
@@ -491,7 +492,7 @@ public class LLUtils {
 	 * cleanup resource
 	 * @param cleanupOnSuccess if true the resource will be cleaned up if the function is successful
 	 */
-	public static <U, T extends Resource<T>, V extends T> Mono<U> usingResource(Mono<V> resourceSupplier,
+	public static <U, T extends Resource<? extends T>, V extends T> Mono<U> usingResource(Mono<V> resourceSupplier,
 			Function<V, Mono<U>> resourceClosure,
 			boolean cleanupOnSuccess) {
 		return Mono.usingWhen(resourceSupplier, resourceClosure, r -> {
diff --git a/src/test/java/it/cavallium/dbengine/StringIndicizer.java b/src/test/java/it/cavallium/dbengine/StringIndicizer.java
index b6a084b..76eb7a5 100644
--- a/src/test/java/it/cavallium/dbengine/StringIndicizer.java
+++ b/src/test/java/it/cavallium/dbengine/StringIndicizer.java
@@ -28,13 +28,13 @@ public class StringIndicizer extends Indicizer<String, String> {
 			var numInt = Ints.tryParse(value);
 			if (numInt != null) {
 				fields.add(LLItem.newIntPoint("intpoint", numInt));
-				fields.add(LLItem.newSortedNumericDocValuesField("intsort", numInt));
+				fields.add(LLItem.newNumericDocValuesField("intsort", numInt));
 			}
 			@SuppressWarnings("UnstableApiUsage")
 			var numLong = Longs.tryParse(value);
 			if (numLong != null) {
 				fields.add(LLItem.newLongPoint("longpoint", numLong));
-				fields.add(LLItem.newSortedNumericDocValuesField("longsort", numLong));
+				fields.add(LLItem.newNumericDocValuesField("longsort", numLong));
 			}
 			return new LLUpdateDocument(fields.toArray(LLItem[]::new));
 		});