Ignore mono elements faster

src/main/java/it/cavallium/dbengine/database/collections/DatabaseMapDictionary.java

@@ -22,6 +22,7 @@ import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.unimi.dsi.fastutil.objects.Object2ObjectLinkedOpenHashMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectSortedMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectSortedMaps;
@@ -228,9 +229,12 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 	public Mono<Object2ObjectSortedMap<T, U>> setAndGetPrevious(Object2ObjectSortedMap<T, U> value) {
 		return this
 				.get(null)
-				.concatWith(dictionary.setRange(rangeMono, Flux
+				.concatWith(dictionary
-						.fromIterable(Collections.unmodifiableMap(value).entrySet())
+						.setRange(rangeMono,
-						.map(entry -> serializeEntry(entry)), true).then(Mono.empty()))
+								Flux.fromIterable(Collections.unmodifiableMap(value).entrySet()).map(entry -> serializeEntry(entry)),
+								true
+						)
+						.as(InternalMonoUtils::toAny))
 				.singleOrEmpty();
 	}
 

src/main/java/it/cavallium/dbengine/database/collections/DatabaseMapDictionaryDeep.java

@@ -22,6 +22,7 @@ import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
 import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.cavallium.dbengine.utils.SimpleResource;
 import it.unimi.dsi.fastutil.objects.Object2ObjectSortedMap;
 import java.util.List;
@@ -362,7 +363,7 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> extend
 				.concatWith(this
 						.clear()
 						.then(this.putMulti(entries))
-						.then(Mono.empty())
+						.as(InternalMonoUtils::toAny)
 				);
 	}
 

src/main/java/it/cavallium/dbengine/database/collections/DatabaseSingleton.java

@@ -14,6 +14,7 @@ import it.cavallium.dbengine.database.UpdateReturnMode;
 import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
 import it.cavallium.dbengine.database.serialization.Serializer;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.cavallium.dbengine.utils.SimpleResource;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -92,7 +93,9 @@ public class DatabaseSingleton<U> extends SimpleResource implements DatabaseStag
 	@Override
 	public Mono<U> setAndGetPrevious(U value) {
 		var resultMono = Flux
-				.concat(singleton.get(null), singleton.set(Mono.fromCallable(() -> serializeValue(value))).then(Mono.empty()))
+				.concat(singleton.get(null),
+						singleton.set(Mono.fromCallable(() -> serializeValue(value))).as(InternalMonoUtils::toAny)
+				)
 				.last();
 		return Mono.usingWhen(resultMono,
 				result -> Mono.fromSupplier(() -> this.deserializeValue(result)),
@@ -154,7 +157,7 @@ public class DatabaseSingleton<U> extends SimpleResource implements DatabaseStag
 
 	@Override
 	public Mono<U> clearAndGetPrevious() {
-		var resultMono = Flux.concat(singleton.get(null), singleton.set(Mono.empty()).then(Mono.empty())).last();
+		var resultMono = Flux.concat(singleton.get(null), singleton.set(Mono.empty()).as(InternalMonoUtils::toAny)).last();
 		return Mono.usingWhen(resultMono,
 				result -> Mono.fromSupplier(() -> this.deserializeValue(result)),
 				LLUtils::finalizeResource

src/main/java/it/cavallium/dbengine/database/memory/LLMemoryDictionary.java

@@ -18,6 +18,7 @@ import it.cavallium.dbengine.database.disk.BinarySerializationFunction;
 import it.cavallium.dbengine.database.serialization.KVSerializationFunction;
 import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.unimi.dsi.fastutil.bytes.ByteList;
 import java.io.IOException;
 import java.util.List;
@@ -91,7 +92,7 @@ public class LLMemoryDictionary implements LLDictionary {
 					.defaultIfEmpty(false)
 					.map((Boolean bool) -> LLUtils.booleanToResponseByteBuffer(allocator, bool));
 		} else {
-			return result.then(Mono.empty());
+			return result.as(InternalMonoUtils::ignoreElements);
 		}
 	}
 

src/main/java/it/cavallium/dbengine/database/memory/LLMemoryKeyValueDatabase.java

@@ -15,6 +15,7 @@ import it.cavallium.dbengine.database.RocksDBStringProperty;
 import it.cavallium.dbengine.database.TableWithProperties;
 import it.cavallium.dbengine.database.UpdateMode;
 import it.cavallium.dbengine.rpc.current.data.Column;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.unimi.dsi.fastutil.bytes.ByteList;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
@@ -76,7 +77,7 @@ public class LLMemoryKeyValueDatabase implements LLKeyValueDatabase {
 							if (defaultValue != null) {
 								return mono.switchIfEmpty(singleton
 										.set(Mono.fromSupplier(() -> allocator.copyOf(defaultValue)))
-										.then(Mono.empty()));
+										.as(InternalMonoUtils::toAny));
 							} else {
 								return mono;
 							}

src/main/java/it/cavallium/dbengine/database/remote/QuicUtils.java

@@ -8,6 +8,7 @@ import it.cavallium.dbengine.database.OptionalBuf;
 import it.cavallium.dbengine.rpc.current.data.RPCCrash;
 import it.cavallium.dbengine.rpc.current.data.RPCEvent;
 import it.cavallium.dbengine.rpc.current.data.nullables.NullableBytes;
+import it.cavallium.dbengine.utils.InternalMonoUtils;
 import it.unimi.dsi.fastutil.bytes.ByteArrayList;
 import it.unimi.dsi.fastutil.bytes.ByteList;
 import java.nio.charset.StandardCharsets;
@@ -241,7 +242,7 @@ public class QuicUtils {
 							.flatMap(updater)
 							.flatMap(stream::send);
 					return Flux
-							.merge(firstRequest, firstResponse.then(Mono.empty()), secondRequest, secondResponse)
+							.merge(firstRequest, firstResponse.as(InternalMonoUtils::ignoreElements), secondRequest, secondResponse)
 							.doFinally(s -> stream.close());
 				})
 				.map(QuicUtils::mapErrors)

src/main/java/it/cavallium/dbengine/utils/InternalMonoUtils.java

@@ -0,0 +1,33 @@
+package it.cavallium.dbengine.utils;
+
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+public class InternalMonoUtils {
+
+
+	@SuppressWarnings("unchecked")
+	public static <ANY> Mono<ANY> toAny(Mono<Void> request) {
+		return (Mono<ANY>) request;
+	}
+
+	@SuppressWarnings("unchecked")
+	public static <ANY> Mono<ANY> toAny(Flux<Void> request) {
+		return (Mono<ANY>) Mono.ignoreElements(request);
+	}
+
+	@SuppressWarnings("unchecked")
+	public static <ANY> Mono<ANY> toAny(Publisher<Void> request) {
+		if (request instanceof Mono<Void> mono) {
+			return (Mono<ANY>) mono;
+		} else {
+			return (Mono<ANY>) Mono.ignoreElements(request);
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	public static <ANY_IN, ANY_OUT> Mono<ANY_OUT> ignoreElements(Publisher<ANY_IN> flux) {
+		return (Mono<ANY_OUT>) Mono.ignoreElements(flux);
+	}
+}