Converted everything to netty direct buffers

pom.xml

@@ -107,7 +107,7 @@
     <dependency>
       <groupId>org.junit.jupiter</groupId>
       <artifactId>junit-jupiter-api</artifactId>
-      <version>5.7.0</version>
+      <version>5.8.0-M1</version>
       <scope>test</scope>
       <exclusions>
         <exclusion>
@@ -116,6 +116,18 @@
         </exclusion>
       </exclusions>
     </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
+      <version>5.8.0-M1</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-params</artifactId>
+      <version>5.8.0-M1</version>
+      <scope>test</scope>
+    </dependency>
     <!-- This will get hamcrest-core automatically -->
     <dependency>
       <groupId>org.hamcrest</groupId>
@@ -138,7 +150,7 @@
     <dependency>
       <groupId>org.rocksdb</groupId>
       <artifactId>rocksdbjni</artifactId>
-      <version>6.16.4</version>
+      <version>6.19.3</version>
     </dependency>
     <dependency>
       <groupId>org.apache.lucene</groupId>

src/main/java/it/cavallium/dbengine/database/LLDatabaseConnection.java

@@ -11,7 +11,7 @@ public interface LLDatabaseConnection {
 
 	Mono<? extends LLDatabaseConnection> connect();
 
-	Mono<? extends LLKeyValueDatabase> getDatabase(String name, List<Column> columns, boolean lowMemory);
+	Mono<? extends LLKeyValueDatabase> getDatabase(String name, List<Column> columns, boolean lowMemory, boolean inMemory);
 
 	Mono<? extends LLLuceneIndex> getLuceneIndex(String name,
 			int instancesCount,
@@ -19,7 +19,8 @@ public interface LLDatabaseConnection {
 			TextFieldsSimilarity textFieldsSimilarity,
 			Duration queryRefreshDebounceTime,
 			Duration commitDebounceTime,
-			boolean lowMemory);
+			boolean lowMemory,
+			boolean inMemory);
 
 	Mono<Void> disconnect();
 }

src/main/java/it/cavallium/dbengine/database/LLDictionary.java

@@ -1,8 +1,9 @@
 package it.cavallium.dbengine.database;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import java.util.List;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
 import org.warp.commonutils.concurrency.atomicity.NotAtomic;
@@ -13,60 +14,62 @@ import reactor.core.publisher.Mono;
 @NotAtomic
 public interface LLDictionary extends LLKeyValueDatabaseStructure {
 
-	Mono<byte[]> get(@Nullable LLSnapshot snapshot, byte[] key, boolean existsAlmostCertainly);
+	ByteBufAllocator getAllocator();
 
-	default Mono<byte[]> get(@Nullable LLSnapshot snapshot, byte[] key) {
+	Mono<ByteBuf> get(@Nullable LLSnapshot snapshot, ByteBuf key, boolean existsAlmostCertainly);
+
+	default Mono<ByteBuf> get(@Nullable LLSnapshot snapshot, ByteBuf key) {
 		return get(snapshot, key, false);
 	}
 
-	Mono<byte[]> put(byte[] key, byte[] value, LLDictionaryResultType resultType);
+	Mono<ByteBuf> put(ByteBuf key, ByteBuf value, LLDictionaryResultType resultType);
 
-	Mono<Boolean> update(byte[] key, Function<Optional<byte[]>, Optional<byte[]>> updater, boolean existsAlmostCertainly);
+	Mono<Boolean> update(ByteBuf key, Function<@Nullable ByteBuf, @Nullable ByteBuf> updater, boolean existsAlmostCertainly);
 
-	default Mono<Boolean> update(byte[] key, Function<Optional<byte[]>, Optional<byte[]>> updater) {
+	default Mono<Boolean> update(ByteBuf key, Function<@Nullable ByteBuf, @Nullable ByteBuf> updater) {
 		return update(key, updater, false);
 	}
 
 	Mono<Void> clear();
 
-	Mono<byte[]> remove(byte[] key, LLDictionaryResultType resultType);
+	Mono<ByteBuf> remove(ByteBuf key, LLDictionaryResultType resultType);
 
-	Flux<Entry<byte[], byte[]>> getMulti(@Nullable LLSnapshot snapshot, Flux<byte[]> keys, boolean existsAlmostCertainly);
+	Flux<Entry<ByteBuf, ByteBuf>> getMulti(@Nullable LLSnapshot snapshot, Flux<ByteBuf> keys, boolean existsAlmostCertainly);
 
-	default Flux<Entry<byte[], byte[]>> getMulti(@Nullable LLSnapshot snapshot, Flux<byte[]> keys) {
+	default Flux<Entry<ByteBuf, ByteBuf>> getMulti(@Nullable LLSnapshot snapshot, Flux<ByteBuf> keys) {
 		return getMulti(snapshot, keys, false);
 	}
 
-	Flux<Entry<byte[], byte[]>> putMulti(Flux<Entry<byte[], byte[]>> entries, boolean getOldValues);
+	Flux<Entry<ByteBuf, ByteBuf>> putMulti(Flux<Entry<ByteBuf, ByteBuf>> entries, boolean getOldValues);
 
-	Flux<Entry<byte[], byte[]>> getRange(@Nullable LLSnapshot snapshot, LLRange range, boolean existsAlmostCertainly);
+	Flux<Entry<ByteBuf, ByteBuf>> getRange(@Nullable LLSnapshot snapshot, LLRange range, boolean existsAlmostCertainly);
 
-	default Flux<Entry<byte[], byte[]>> getRange(@Nullable LLSnapshot snapshot, LLRange range) {
+	default Flux<Entry<ByteBuf, ByteBuf>> getRange(@Nullable LLSnapshot snapshot, LLRange range) {
 		return getRange(snapshot, range, false);
 	}
 
-	Flux<List<Entry<byte[], byte[]>>> getRangeGrouped(@Nullable LLSnapshot snapshot,
+	Flux<List<Entry<ByteBuf, ByteBuf>>> getRangeGrouped(@Nullable LLSnapshot snapshot,
 			LLRange range,
 			int prefixLength,
 			boolean existsAlmostCertainly);
 
-	default Flux<List<Entry<byte[], byte[]>>> getRangeGrouped(@Nullable LLSnapshot snapshot,
+	default Flux<List<Entry<ByteBuf, ByteBuf>>> getRangeGrouped(@Nullable LLSnapshot snapshot,
 			LLRange range,
 			int prefixLength) {
 		return getRangeGrouped(snapshot, range, prefixLength, false);
 	}
 
-	Flux<byte[]> getRangeKeys(@Nullable LLSnapshot snapshot, LLRange range);
+	Flux<ByteBuf> getRangeKeys(@Nullable LLSnapshot snapshot, LLRange range);
 
-	Flux<List<byte[]>> getRangeKeysGrouped(@Nullable LLSnapshot snapshot, LLRange range, int prefixLength);
+	Flux<List<ByteBuf>> getRangeKeysGrouped(@Nullable LLSnapshot snapshot, LLRange range, int prefixLength);
 
-	Flux<byte[]> getRangeKeyPrefixes(@Nullable LLSnapshot snapshot, LLRange range, int prefixLength);
+	Flux<ByteBuf> getRangeKeyPrefixes(@Nullable LLSnapshot snapshot, LLRange range, int prefixLength);
 
-	Flux<Entry<byte[], byte[]>> setRange(LLRange range, Flux<Entry<byte[], byte[]>> entries, boolean getOldValues);
+	Flux<Entry<ByteBuf, ByteBuf>> setRange(LLRange range, Flux<Entry<ByteBuf, ByteBuf>> entries, boolean getOldValues);
 
 	default Mono<Void> replaceRange(LLRange range,
 			boolean canKeysChange,
-			Function<Entry<byte[], byte[]>, Mono<Entry<byte[], byte[]>>> entriesReplacer,
+			Function<Entry<ByteBuf, ByteBuf>, Mono<Entry<ByteBuf, ByteBuf>>> entriesReplacer,
 			boolean existsAlmostCertainly) {
 		return Mono.defer(() -> {
 			if (canKeysChange) {
@@ -87,7 +90,7 @@ public interface LLDictionary extends LLKeyValueDatabaseStructure {
 
 	default Mono<Void> replaceRange(LLRange range,
 			boolean canKeysChange,
-			Function<Entry<byte[], byte[]>, Mono<Entry<byte[], byte[]>>> entriesReplacer) {
+			Function<Entry<ByteBuf, ByteBuf>, Mono<Entry<ByteBuf, ByteBuf>>> entriesReplacer) {
 		return replaceRange(range, canKeysChange, entriesReplacer, false);
 	}
 
@@ -95,9 +98,9 @@ public interface LLDictionary extends LLKeyValueDatabaseStructure {
 
 	Mono<Long> sizeRange(@Nullable LLSnapshot snapshot, LLRange range, boolean fast);
 
-	Mono<Entry<byte[], byte[]>> getOne(@Nullable LLSnapshot snapshot, LLRange range);
+	Mono<Entry<ByteBuf, ByteBuf>> getOne(@Nullable LLSnapshot snapshot, LLRange range);
 
-	Mono<byte[]> getOneKey(@Nullable LLSnapshot snapshot, LLRange range);
+	Mono<ByteBuf> getOneKey(@Nullable LLSnapshot snapshot, LLRange range);
 
-	Mono<Entry<byte[], byte[]>> removeOne(LLRange range);
+	Mono<Entry<ByteBuf, ByteBuf>> removeOne(LLRange range);
 }

src/main/java/it/cavallium/dbengine/database/LLDictionaryResultType.java

@@ -1,5 +1,5 @@
 package it.cavallium.dbengine.database;
 
 public enum LLDictionaryResultType {
-	VOID, VALUE_CHANGED, PREVIOUS_VALUE
+	VOID, PREVIOUS_VALUE_EXISTENCE, PREVIOUS_VALUE
 }

src/main/java/it/cavallium/dbengine/database/LLRange.java

@@ -1,5 +1,10 @@
 package it.cavallium.dbengine.database;
 
+import static io.netty.buffer.Unpooled.wrappedBuffer;
+import static io.netty.buffer.Unpooled.wrappedUnmodifiableBuffer;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
 import java.util.Arrays;
 import java.util.StringJoiner;
 
@@ -9,10 +14,18 @@ import java.util.StringJoiner;
 public class LLRange {
 
 	private static final LLRange RANGE_ALL = new LLRange(null, null);
-	private final byte[] min;
-	private final byte[] max;
+	private final ByteBuf min;
+	private final ByteBuf max;
 
-	private LLRange(byte[] min, byte[] max) {
+	private LLRange(ByteBuf min, ByteBuf max) {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
+		if (min != null && !min.isDirect()) {
+			throw new IllegalArgumentException("Min buffer must be direct");
+		}
+		if (max != null && !max.isDirect()) {
+			throw new IllegalArgumentException("Min buffer must be direct");
+		}
 		this.min = min;
 		this.max = max;
 	}
@@ -21,50 +34,64 @@ public class LLRange {
 		return RANGE_ALL;
 	}
 
-	public static LLRange from(byte[] min) {
+	public static LLRange from(ByteBuf min) {
 		return new LLRange(min, null);
 	}
 
-	public static LLRange to(byte[] max) {
+	public static LLRange to(ByteBuf max) {
 		return new LLRange(null, max);
 	}
 
-	public static LLRange single(byte[] single) {
+	public static LLRange single(ByteBuf single) {
 		return new LLRange(single, single);
 	}
 
-	public static LLRange of(byte[] min, byte[] max) {
+	public static LLRange of(ByteBuf min, ByteBuf max) {
 		return new LLRange(min, max);
 	}
 
 	public boolean isAll() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		return min == null && max == null;
 	}
 
 	public boolean isSingle() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		if (min == null || max == null) return false;
-		return Arrays.equals(min, max);
+		return LLUtils.equals(min, max);
 	}
 
 	public boolean hasMin() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		return min != null;
 	}
 
-	public byte[] getMin() {
+	public ByteBuf getMin() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		assert min != null;
 		return min;
 	}
 
 	public boolean hasMax() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		return max != null;
 	}
 
-	public byte[] getMax() {
+	public ByteBuf getMax() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		assert max != null;
 		return max;
 	}
 
-	public byte[] getSingle() {
+	public ByteBuf getSingle() {
+		assert min == null || min.refCnt() > 0;
+		assert max == null || max.refCnt() > 0;
 		assert isSingle();
 		return min;
 	}
@@ -78,21 +105,40 @@ public class LLRange {
 			return false;
 		}
 		LLRange llRange = (LLRange) o;
-		return Arrays.equals(min, llRange.min) && Arrays.equals(max, llRange.max);
+		return LLUtils.equals(min, llRange.min) && LLUtils.equals(max, llRange.max);
 	}
 
 	@Override
 	public int hashCode() {
-		int result = Arrays.hashCode(min);
-		result = 31 * result + Arrays.hashCode(max);
+		int result = LLUtils.hashCode(min);
+		result = 31 * result + LLUtils.hashCode(max);
 		return result;
 	}
 
 	@Override
 	public String toString() {
 		return new StringJoiner(", ", LLRange.class.getSimpleName() + "[", "]")
-				.add("min=" + Arrays.toString(min))
-				.add("max=" + Arrays.toString(max))
+				.add("min=" + LLUtils.toString(min))
+				.add("max=" + LLUtils.toString(max))
 				.toString();
 	}
+
+	public LLRange retain() {
+		if (min != null) {
+			min.retain();
+		}
+		if (max != null) {
+			max.retain();
+		}
+		return this;
+	}
+
+	public void release() {
+		if (min != null) {
+			min.release();
+		}
+		if (max != null) {
+			max.release();
+		}
+	}
 }

src/main/java/it/cavallium/dbengine/database/LLUtils.java

@@ -2,10 +2,18 @@ package it.cavallium.dbengine.database;
 
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
+import io.netty.buffer.AbstractByteBufAllocator;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.buffer.CompositeByteBuf;
+import io.netty.buffer.PooledByteBufAllocator;
 import it.cavallium.dbengine.lucene.RandomSortField;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.function.ToIntFunction;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.FloatPoint;
@@ -20,13 +28,20 @@ import org.apache.lucene.search.ScoreMode;
 import org.apache.lucene.search.Sort;
 import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.SortedNumericSortField;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.rocksdb.RocksDB;
+
+import static io.netty.buffer.Unpooled.EMPTY_BUFFER;
+import static io.netty.buffer.Unpooled.wrappedBuffer;
 
 @SuppressWarnings("unused")
 public class LLUtils {
 
 	private static final byte[] RESPONSE_TRUE = new byte[]{1};
 	private static final byte[] RESPONSE_FALSE = new byte[]{0};
+	private static final byte[] RESPONSE_TRUE_BUF = new byte[]{1};
+	private static final byte[] RESPONSE_FALSE_BUF = new byte[]{0};
 	public static final byte[][] LEXICONOGRAPHIC_ITERATION_SEEKS = new byte[256][1];
 
 	static {
@@ -40,10 +55,23 @@ public class LLUtils {
 		return response[0] == 1;
 	}
 
+	public static boolean responseToBoolean(ByteBuf response) {
+		try {
+			assert response.readableBytes() == 1;
+			return response.getByte(response.readerIndex()) == 1;
+		} finally {
+			response.release();
+		}
+	}
+
 	public static byte[] booleanToResponse(boolean bool) {
 		return bool ? RESPONSE_TRUE : RESPONSE_FALSE;
 	}
 
+	public static ByteBuf booleanToResponseByteBuffer(boolean bool) {
+		return wrappedBuffer(booleanToResponse(bool));
+	}
+
 	@Nullable
 	public static Sort toSort(@Nullable LLSort sort) {
 		if (sort == null) {
@@ -127,4 +155,228 @@ public class LLUtils {
 	public static it.cavallium.dbengine.database.LLKeyScore toKeyScore(LLKeyScore hit) {
 		return new it.cavallium.dbengine.database.LLKeyScore(hit.getKey(), hit.getScore());
 	}
+
+	public static String toString(ByteBuf key) {
+		if (key == null) {
+			return "null";
+		} else {
+			int startIndex = key.readerIndex();
+			int iMax = key.readableBytes() - 1;
+			int iLimit = 128;
+			if (iMax <= -1) {
+				return "[]";
+			} else {
+				StringBuilder b = new StringBuilder();
+				b.append('[');
+				int i = 0;
+
+				while(true) {
+					b.append(key.getByte(startIndex + i));
+					if (i == iLimit) {
+						b.append("…");
+					}
+					if (i == iMax || i == iLimit) {
+						return b.append(']').toString();
+					}
+
+					b.append(", ");
+					++i;
+				}
+			}
+		}
+	}
+
+	public static boolean equals(ByteBuf a, ByteBuf b) {
+		if (a == null && b == null) {
+			return true;
+		} else if (a != null && b != null) {
+			return ByteBufUtil.equals(a, b);
+		} else {
+			return false;
+		}
+	}
+
+	public static byte[] toArray(ByteBuf key) {
+		byte[] keyBytes = new byte[key.readableBytes()];
+		key.getBytes(key.readerIndex(), keyBytes, 0, key.readableBytes());
+		return keyBytes;
+	}
+
+	public static List<byte[]> toArray(List<ByteBuf> input) {
+		List<byte[]> result = new ArrayList<>(input.size());
+		for (ByteBuf byteBuf : input) {
+			result.add(toArray(byteBuf));
+		}
+		return result;
+	}
+
+	public static int hashCode(ByteBuf buf) {
+		return buf == null ? 0 : buf.hashCode();
+	}
+
+	@Nullable
+	public static ByteBuf readNullableDirectNioBuffer(ByteBufAllocator alloc, ToIntFunction<ByteBuffer> reader) {
+		ByteBuf buffer = alloc.directBuffer();
+		try {
+			ByteBuf directBuffer = null;
+			ByteBuffer nioBuffer;
+			int size;
+			Boolean mustBeCopied = null;
+			do {
+				if (mustBeCopied == null || !mustBeCopied) {
+					nioBuffer = LLUtils.toDirectFast(buffer.retain());
+					if (nioBuffer != null) {
+						nioBuffer.limit(nioBuffer.capacity());
+					}
+				} else {
+					nioBuffer = null;
+				}
+				if ((mustBeCopied != null && mustBeCopied) || nioBuffer == null) {
+					directBuffer = LLUtils.toDirectCopy(buffer.retain());
+					nioBuffer = directBuffer.nioBuffer(0, directBuffer.capacity());
+					mustBeCopied = true;
+				} else {
+					mustBeCopied = false;
+				}
+				try {
+					assert nioBuffer.isDirect();
+					size = reader.applyAsInt(nioBuffer);
+					if (size != RocksDB.NOT_FOUND) {
+						if (mustBeCopied) {
+							buffer.writerIndex(0).writeBytes(nioBuffer);
+						}
+						if (size == nioBuffer.limit()) {
+							buffer.setIndex(0, size);
+							return buffer;
+						} else {
+							assert size > nioBuffer.limit();
+							assert nioBuffer.limit() > 0;
+							buffer.capacity(size);
+						}
+					}
+				} finally {
+					if (nioBuffer != null) {
+						nioBuffer = null;
+					}
+					if(directBuffer != null) {
+						directBuffer.release();
+						directBuffer = null;
+					}
+				}
+			} while (size != RocksDB.NOT_FOUND);
+		} catch (Throwable t) {
+			buffer.release();
+			throw t;
+		}
+		return null;
+	}
+
+	@Nullable
+	public static ByteBuffer toDirectFast(ByteBuf buffer) {
+		try {
+			ByteBuffer result = buffer.nioBuffer(0, buffer.capacity());
+			if (result.isDirect()) {
+				result.limit(buffer.writerIndex());
+
+				assert result.isDirect();
+				assert result.capacity() == buffer.capacity();
+				assert buffer.readerIndex() == result.position();
+				assert result.limit() - result.position() == buffer.readableBytes();
+
+				return result;
+			} else {
+				return null;
+			}
+		} finally {
+			buffer.release();
+		}
+	}
+
+	public static ByteBuf toDirectCopy(ByteBuf buffer) {
+		try {
+			ByteBuf directCopyBuf = buffer.alloc().directBuffer(buffer.capacity(), buffer.maxCapacity());
+			directCopyBuf.writeBytes(buffer, 0, buffer.writerIndex());
+			return directCopyBuf;
+		} finally {
+			buffer.release();
+		}
+	}
+
+	public static ByteBuf convertToDirectByteBuf(AbstractByteBufAllocator alloc, ByteBuf buffer) {
+		ByteBuf result;
+		ByteBuf directCopyBuf = alloc.directBuffer(buffer.capacity(), buffer.maxCapacity());
+		directCopyBuf.writeBytes(buffer, 0, buffer.writerIndex());
+		directCopyBuf.readerIndex(buffer.readerIndex());
+		result = directCopyBuf;
+		assert result.isDirect();
+		assert result.capacity() == buffer.capacity();
+		assert buffer.readerIndex() == result.readerIndex();
+		return result;
+	}
+
+	@NotNull
+	public static ByteBuf readDirectNioBuffer(ByteBufAllocator alloc, ToIntFunction<ByteBuffer> reader) {
+		var buffer = readNullableDirectNioBuffer(alloc, reader);
+		if (buffer == null) {
+			throw new IllegalStateException("A non-nullable buffer read operation tried to return a \"not found\" element");
+		}
+		return buffer;
+	}
+
+	public static ByteBuf directCompositeBuffer(ByteBufAllocator alloc, ByteBuf buffer) {
+		return wrappedBuffer(buffer);
+	}
+
+	public static ByteBuf directCompositeBuffer(ByteBufAllocator alloc, ByteBuf buffer1, ByteBuf buffer2) {
+		assert buffer1.isDirect();
+		assert buffer1.nioBuffer().isDirect();
+		assert buffer2.isDirect();
+		assert buffer2.nioBuffer().isDirect();
+		if (buffer1.readableBytes() == 0) {
+			return wrappedBuffer(buffer2);
+		} else if (buffer2.readableBytes() == 0) {
+			return wrappedBuffer(buffer1);
+		}
+		CompositeByteBuf compositeBuffer = alloc.compositeDirectBuffer(2);
+		compositeBuffer.addComponent(true, buffer1);
+		compositeBuffer.addComponent(true, buffer2);
+		compositeBuffer.consolidate();
+		assert compositeBuffer.isDirect();
+		assert compositeBuffer.nioBuffer().isDirect();
+		return compositeBuffer;
+	}
+
+	public static ByteBuf directCompositeBuffer(ByteBufAllocator alloc, ByteBuf buffer1, ByteBuf buffer2, ByteBuf buffer3) {
+		if (buffer1.readableBytes() == 0) {
+			return directCompositeBuffer(alloc, buffer2, buffer3);
+		} else if (buffer2.readableBytes() == 0) {
+			return directCompositeBuffer(alloc, buffer1, buffer3);
+		} else if (buffer3.readableBytes() == 0) {
+			return directCompositeBuffer(alloc, buffer1, buffer2);
+		}
+		CompositeByteBuf compositeBuffer = alloc.compositeDirectBuffer(3);
+		compositeBuffer.addComponent(true, buffer1);
+		compositeBuffer.addComponent(true, buffer2);
+		compositeBuffer.addComponent(true, buffer3);
+		compositeBuffer.consolidate();
+		return compositeBuffer;
+	}
+
+	public static ByteBuf directCompositeBuffer(ByteBufAllocator alloc, ByteBuf... buffers) {
+		switch (buffers.length) {
+			case 0:
+				return EMPTY_BUFFER;
+			case 1:
+				return directCompositeBuffer(alloc, buffers[0]);
+			case 2:
+				return directCompositeBuffer(alloc, buffers[0], buffers[1]);
+			case 3:
+				return directCompositeBuffer(alloc, buffers[0], buffers[1], buffers[2]);
+			default:
+				CompositeByteBuf compositeBuffer = alloc.compositeDirectBuffer(buffers.length);
+				compositeBuffer.addComponents(true, buffers);
+				compositeBuffer.consolidate();
+				return compositeBuffer;
+		}
+	}
 }

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

@@ -1,24 +1,25 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import java.util.function.Function;
 import org.jetbrains.annotations.NotNull;
+import static io.netty.buffer.Unpooled.*;
 
 public class DatabaseEmpty {
 
 	@SuppressWarnings({"unused", "InstantiationOfUtilityClass"})
 	public static final Nothing NOTHING = new Nothing();
-	private static final byte[] NOTHING_BYTES = new byte[0];
-	public static final Serializer<Nothing, byte[]> NOTHING_SERIALIZER = new Serializer<>() {
+	public static final Serializer<Nothing, ByteBuf> NOTHING_SERIALIZER = new Serializer<>() {
 		@Override
-		public @NotNull Nothing deserialize(byte @NotNull [] serialized) {
+		public @NotNull Nothing deserialize(@NotNull ByteBuf serialized) {
 			return NOTHING;
 		}
 
 		@Override
-		public byte @NotNull [] serialize(@NotNull Nothing deserialized) {
-			return NOTHING_BYTES;
+		public @NotNull ByteBuf serialize(@NotNull Nothing deserialized) {
+			return EMPTY_BUFFER;
 		}
 	};
 	public static final Function<Nothing, Nothing> NOTHING_HASH_FUNCTION = nothing -> nothing;
@@ -28,7 +29,7 @@ public class DatabaseEmpty {
 	private DatabaseEmpty() {
 	}
 
-	public static DatabaseStageEntry<Nothing> create(LLDictionary dictionary, byte[] key) {
+	public static DatabaseStageEntry<Nothing> create(LLDictionary dictionary, ByteBuf key) {
 		return new DatabaseSingle<>(dictionary, key, NOTHING_SERIALIZER);
 	}
 

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

@@ -1,18 +1,19 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.LLDictionaryResultType;
 import it.cavallium.dbengine.database.LLUtils;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
-import java.util.Arrays;
+import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
+import org.rocksdb.RocksDBException;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -21,40 +22,44 @@ import reactor.core.publisher.Mono;
  */
 public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U, DatabaseStageEntry<U>> {
 
-	private final Serializer<U, byte[]> valueSerializer;
+	private final Serializer<U, ByteBuf> valueSerializer;
 
 	protected DatabaseMapDictionary(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer,
-			Serializer<U, byte[]> valueSerializer) {
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer,
+			Serializer<U, ByteBuf> valueSerializer) {
+		// Do not retain or release or use the prefixKey here
 		super(dictionary, prefixKey, keySuffixSerializer, new SubStageGetterSingle<>(valueSerializer), 0);
+		prefixKey = null;
 		this.valueSerializer = valueSerializer;
 	}
 
 	public static <T, U> DatabaseMapDictionary<T, U> simple(LLDictionary dictionary,
-			SerializerFixedBinaryLength<T, byte[]> keySerializer,
-			Serializer<U, byte[]> valueSerializer) {
+			SerializerFixedBinaryLength<T, ByteBuf> keySerializer,
+			Serializer<U, ByteBuf> valueSerializer) {
 		return new DatabaseMapDictionary<>(dictionary, EMPTY_BYTES, keySerializer, valueSerializer);
 	}
 
 	public static <T, U> DatabaseMapDictionary<T, U> tail(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer,
-			Serializer<U, byte[]> valueSerializer) {
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer,
+			Serializer<U, ByteBuf> valueSerializer) {
 		return new DatabaseMapDictionary<>(dictionary, prefixKey, keySuffixSerializer, valueSerializer);
 	}
 
-	private byte[] toKey(byte[] suffixKey) {
-		assert suffixKeyConsistency(suffixKey.length);
-		byte[] key = Arrays.copyOf(keyPrefix, keyPrefix.length + suffixKey.length);
-		System.arraycopy(suffixKey, 0, key, keyPrefix.length, suffixKey.length);
-		return key;
+	private ByteBuf toKey(ByteBuf suffixKey) {
+		assert suffixKeyConsistency(suffixKey.readableBytes());
+		try {
+			return LLUtils.directCompositeBuffer(dictionary.getAllocator(), keyPrefix.retain(), suffixKey.retain());
+		} finally {
+			suffixKey.release();
+		}
 	}
 
 	@Override
 	public Mono<Map<T, U>> get(@Nullable CompositeSnapshot snapshot, boolean existsAlmostCertainly) {
 		return dictionary
-				.getRange(resolveSnapshot(snapshot), range, existsAlmostCertainly)
+				.getRange(resolveSnapshot(snapshot), range.retain(), existsAlmostCertainly)
 				.collectMap(
 						entry -> deserializeSuffix(stripPrefix(entry.getKey())),
 						entry -> deserialize(entry.getValue()),
@@ -64,7 +69,7 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 	@Override
 	public Mono<Map<T, U>> setAndGetPrevious(Map<T, U> value) {
 		return dictionary
-				.setRange(range,
+				.setRange(range.retain(),
 						Flux
 								.fromIterable(value.entrySet())
 								.map(entry -> Map.entry(serializeSuffix(entry.getKey()), serialize(entry.getValue()))),
@@ -79,7 +84,7 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 	@Override
 	public Mono<Map<T, U>> clearAndGetPrevious() {
 		return dictionary
-				.setRange(range, Flux.empty(), true)
+				.setRange(range.retain(), Flux.empty(), true)
 				.collectMap(
 						entry -> deserializeSuffix(stripPrefix(entry.getKey())),
 						entry -> deserialize(entry.getValue()),
@@ -88,96 +93,170 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 
 	@Override
 	public Mono<Long> leavesCount(@Nullable CompositeSnapshot snapshot, boolean fast) {
-		return dictionary.sizeRange(resolveSnapshot(snapshot), range, fast);
+		return dictionary.sizeRange(resolveSnapshot(snapshot), range.retain(), fast);
 	}
 
 	@Override
 	public Mono<Boolean> isEmpty(@Nullable CompositeSnapshot snapshot) {
-		return dictionary.isRangeEmpty(resolveSnapshot(snapshot), range);
+		return dictionary.isRangeEmpty(resolveSnapshot(snapshot), range.retain());
 	}
 
 	@Override
 	public Mono<DatabaseStageEntry<U>> at(@Nullable CompositeSnapshot snapshot, T keySuffix) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
 		return Mono
-				.just(new DatabaseSingle<>(dictionary, toKey(serializeSuffix(keySuffix)), Serializer.noop()))
-				.map(entry -> new DatabaseSingleMapped<>(entry, valueSerializer));
+				.fromSupplier(() -> new DatabaseSingle<>(dictionary, keyBuf.retain(), Serializer.noop()))
+				.<DatabaseStageEntry<U>>map(entry -> new DatabaseSingleMapped<>(entry, valueSerializer))
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+				});
 	}
 
 	@Override
 	public Mono<U> getValue(@Nullable CompositeSnapshot snapshot, T keySuffix, boolean existsAlmostCertainly) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
 		return dictionary
-				.get(resolveSnapshot(snapshot), toKey(serializeSuffix(keySuffix)), existsAlmostCertainly)
-				.map(this::deserialize);
+				.get(resolveSnapshot(snapshot), keyBuf.retain(), existsAlmostCertainly)
+				.map(this::deserialize)
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+				});
 	}
 
 	@Override
 	public Mono<Void> putValue(T keySuffix, U value) {
-		return dictionary.put(toKey(serializeSuffix(keySuffix)), serialize(value), LLDictionaryResultType.VOID).then();
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
+		ByteBuf valueBuf = serialize(value);
+		return dictionary.put(keyBuf.retain(), valueBuf.retain(), LLDictionaryResultType.VOID).doFinally(s -> {
+			keyBuf.release();
+			keySuffixBuf.release();
+			valueBuf.release();
+		}).then();
 	}
 
 	@Override
 	public Mono<Boolean> updateValue(T keySuffix,
 			boolean existsAlmostCertainly,
-			Function<Optional<U>, Optional<U>> updater) {
-		return dictionary.update(toKey(serializeSuffix(keySuffix)),
-				oldSerialized -> updater.apply(oldSerialized.map(this::deserialize)).map(this::serialize),
-				existsAlmostCertainly
-		);
+			Function<@Nullable U, @Nullable U> updater) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
+		return dictionary.update(keyBuf.retain(), oldSerialized -> {
+			try {
+				var result = updater.apply(oldSerialized == null ? null : this.deserialize(oldSerialized.retain()));
+				if (result == null) {
+					return null;
+				} else {
+					return this.serialize(result);
+				}
+			} finally {
+				if (oldSerialized != null) {
+					oldSerialized.release();
+				}
+			}
+		}, existsAlmostCertainly).doFinally(s -> {
+			keyBuf.release();
+			keySuffixBuf.release();
+		});
 	}
 
 	@Override
 	public Mono<U> putValueAndGetPrevious(T keySuffix, U value) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
+		ByteBuf valueBuf = serialize(value);
 		return dictionary
-				.put(toKey(serializeSuffix(keySuffix)), serialize(value), LLDictionaryResultType.PREVIOUS_VALUE)
-				.map(this::deserialize);
+				.put(keyBuf.retain(), valueBuf.retain(), LLDictionaryResultType.PREVIOUS_VALUE)
+				.map(this::deserialize)
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+					valueBuf.release();
+				});
 	}
 
 	@Override
 	public Mono<Boolean> putValueAndGetStatus(T keySuffix, U value) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
+		ByteBuf valueBuf = serialize(value);
 		return dictionary
-				.put(toKey(serializeSuffix(keySuffix)), serialize(value), LLDictionaryResultType.VALUE_CHANGED)
-				.map(LLUtils::responseToBoolean);
+				.put(keyBuf.retain(), valueBuf.retain(), LLDictionaryResultType.PREVIOUS_VALUE_EXISTENCE)
+				.map(LLUtils::responseToBoolean)
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+					valueBuf.release();
+				});
 	}
 
 	@Override
 	public Mono<Void> remove(T keySuffix) {
-		return dictionary.remove(toKey(serializeSuffix(keySuffix)), LLDictionaryResultType.VOID).then();
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
+		return dictionary.remove(keyBuf.retain(), LLDictionaryResultType.VOID).doFinally(s -> {
+			keyBuf.release();
+			keySuffixBuf.release();
+		}).then();
 	}
 
 	@Override
 	public Mono<U> removeAndGetPrevious(T keySuffix) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
 		return dictionary
-				.remove(toKey(serializeSuffix(keySuffix)), LLDictionaryResultType.PREVIOUS_VALUE)
-				.map(this::deserialize);
+				.remove(keyBuf.retain(), LLDictionaryResultType.PREVIOUS_VALUE)
+				.map(this::deserialize)
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+				});
 	}
 
 	@Override
 	public Mono<Boolean> removeAndGetStatus(T keySuffix) {
+		ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+		ByteBuf keyBuf = toKey(keySuffixBuf.retain());
 		return dictionary
-				.remove(toKey(serializeSuffix(keySuffix)), LLDictionaryResultType.VALUE_CHANGED)
-				.map(LLUtils::responseToBoolean);
+				.remove(keyBuf.retain(), LLDictionaryResultType.PREVIOUS_VALUE_EXISTENCE)
+				.map(LLUtils::responseToBoolean)
+				.doFinally(s -> {
+					keyBuf.release();
+					keySuffixBuf.release();
+				});
 	}
 
 	@Override
 	public Flux<Entry<T, U>> getMulti(@Nullable CompositeSnapshot snapshot, Flux<T> keys, boolean existsAlmostCertainly) {
 		return dictionary
-				.getMulti(resolveSnapshot(snapshot), keys.map(keySuffix -> toKey(serializeSuffix(keySuffix))), existsAlmostCertainly)
-				.map(entry -> Map.entry(deserializeSuffix(stripPrefix(entry.getKey())), deserialize(entry.getValue())));
+				.getMulti(resolveSnapshot(snapshot), keys.flatMap(keySuffix -> Mono.fromCallable(() -> {
+					ByteBuf keySuffixBuf = serializeSuffix(keySuffix);
+					try {
+						return toKey(keySuffixBuf.retain());
+					} finally {
+						keySuffixBuf.release();
+					}
+				})), existsAlmostCertainly)
+				.flatMap(entry -> Mono.fromCallable(() -> Map.entry(deserializeSuffix(stripPrefix(entry.getKey())), deserialize(entry.getValue()))));
 	}
 
 	@Override
 	public Mono<Void> putMulti(Flux<Entry<T, U>> entries) {
 		return dictionary
-				.putMulti(entries
-						.map(entry -> Map
-								.entry(toKey(serializeSuffix(entry.getKey())), serialize(entry.getValue()))), false)
+				.putMulti(entries.flatMap(entry -> Mono.fromCallable(() -> Map.entry(toKey(serializeSuffix(entry.getKey())),
+						serialize(entry.getValue())
+				))), false)
 				.then();
 	}
 
 	@Override
 	public Flux<Entry<T, DatabaseStageEntry<U>>> getAllStages(@Nullable CompositeSnapshot snapshot) {
 		return dictionary
-				.getRangeKeys(resolveSnapshot(snapshot), range)
+				.getRangeKeys(resolveSnapshot(snapshot), range.retain())
 				.map(key -> Map.entry(deserializeSuffix(stripPrefix(key)),
 						new DatabaseSingleMapped<>(
 								new DatabaseSingle<>(dictionary,
@@ -191,7 +270,7 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 	@Override
 	public Flux<Entry<T, U>> getAllValues(@Nullable CompositeSnapshot snapshot) {
 		return dictionary
-				.getRange(resolveSnapshot(snapshot), range)
+				.getRange(resolveSnapshot(snapshot), range.retain())
 				.map(serializedEntry -> Map.entry(
 						deserializeSuffix(stripPrefix(serializedEntry.getKey())),
 						valueSerializer.deserialize(serializedEntry.getValue())
@@ -201,7 +280,7 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 	@Override
 	public Flux<Entry<T, U>> setAllValuesAndGetPrevious(Flux<Entry<T, U>> entries) {
 		return dictionary
-				.setRange(range,
+				.setRange(range.retain(),
 						entries.map(entry ->
 								Map.entry(toKey(serializeSuffix(entry.getKey())), serialize(entry.getValue()))), true)
 				.map(entry -> Map.entry(deserializeSuffix(stripPrefix(entry.getKey())), deserialize(entry.getValue())));
@@ -214,22 +293,31 @@ public class DatabaseMapDictionary<T, U> extends DatabaseMapDictionaryDeep<T, U,
 					.clear();
 		} else if (range.isSingle()) {
 			return dictionary
-					.remove(range.getSingle(), LLDictionaryResultType.VOID)
+					.remove(range.getSingle().retain(), LLDictionaryResultType.VOID)
 					.then();
 		} else {
 			return dictionary
-					.setRange(range, Flux.empty(), false)
+					.setRange(range.retain(), Flux.empty(), false)
 					.then();
 		}
 	}
 
-	//todo: temporary wrapper. convert the whole class to buffers
-	private U deserialize(byte[] bytes) {
+	/**
+	 * This method is just a shorter version than valueSerializer::deserialize
+	 */
+	private U deserialize(ByteBuf bytes) {
 		return valueSerializer.deserialize(bytes);
 	}
 
-	//todo: temporary wrapper. convert the whole class to buffers
-	private byte[] serialize(U bytes) {
+	/**
+	 * This method is just a shorter version than valueSerializer::serialize
+	 */
+	private ByteBuf serialize(U bytes) {
 		return valueSerializer.serialize(bytes);
 	}
+
+	@Override
+	public void release() {
+		super.release();
+	}
 }

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

@@ -1,10 +1,15 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.buffer.PooledByteBufAllocator;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.LLDictionaryResultType;
 import it.cavallium.dbengine.database.LLRange;
 import it.cavallium.dbengine.database.LLSnapshot;
+import it.cavallium.dbengine.database.LLUtils;
 import it.cavallium.dbengine.database.disk.LLLocalDictionary;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
 import java.util.Arrays;
@@ -14,88 +19,162 @@ import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.util.function.Tuples;
+import static io.netty.buffer.Unpooled.*;
 
 // todo: implement optimized methods
 public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implements DatabaseStageMap<T, U, US> {
 
-	public static final byte[] EMPTY_BYTES = new byte[0];
+	public static final ByteBuf EMPTY_BYTES = unreleasableBuffer(directBuffer(0, 0));
 	protected final LLDictionary dictionary;
+	private final ByteBufAllocator alloc;
 	protected final SubStageGetter<U, US> subStageGetter;
-	protected final SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer;
-	protected final byte[] keyPrefix;
+	protected final SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer;
+	protected final ByteBuf keyPrefix;
+	protected final int keyPrefixLength;
 	protected final int keySuffixLength;
 	protected final int keyExtLength;
 	protected final LLRange range;
 
-	private static byte[] incrementPrefix(byte[] key, int prefixLength) {
-		boolean remainder = true;
-		final byte ff = (byte) 0xFF;
-		for (int i = prefixLength - 1; i >= 0; i--) {
-			if (key[i] != ff) {
-				key[i]++;
-				remainder = false;
-				break;
-			} else {
-				key[i] = 0x00;
-				remainder = true;
+	private static ByteBuf incrementPrefix(ByteBufAllocator alloc, ByteBuf originalKey, int prefixLength) {
+		try {
+			assert originalKey.readableBytes() >= prefixLength;
+			ByteBuf copiedBuf = alloc.directBuffer(originalKey.writerIndex(), originalKey.writerIndex() + 1);
+			try {
+				boolean overflowed = true;
+				final int ff = 0xFF;
+				int writtenBytes = 0;
+				copiedBuf.writerIndex(prefixLength);
+				for (int i = prefixLength - 1; i >= 0; i--) {
+					int iByte = originalKey.getUnsignedByte(i);
+					if (iByte != ff) {
+						copiedBuf.setByte(i, iByte + 1);
+						writtenBytes++;
+						overflowed = false;
+						break;
+					} else {
+						copiedBuf.setByte(i, 0x00);
+						writtenBytes++;
+						overflowed = true;
+					}
+				}
+				assert prefixLength - writtenBytes >= 0;
+				if (prefixLength - writtenBytes > 0) {
+					copiedBuf.setBytes(0, originalKey, 0, (prefixLength - writtenBytes));
+				}
+
+				copiedBuf.writerIndex(copiedBuf.capacity());
+
+				if (originalKey.writerIndex() - prefixLength > 0) {
+					copiedBuf.setBytes(prefixLength, originalKey, prefixLength, originalKey.writerIndex() - prefixLength);
+				}
+
+				if (overflowed) {
+					for (int i = 0; i < copiedBuf.writerIndex(); i++) {
+						copiedBuf.setByte(i, 0xFF);
+					}
+					copiedBuf.writeZero(1);
+				}
+				return copiedBuf.retain();
+			} finally {
+				copiedBuf.release();
 			}
-		}
-
-		if (remainder) {
-			Arrays.fill(key, 0, prefixLength, (byte) 0xFF);
-			return Arrays.copyOf(key, key.length + 1);
-		} else {
-			return key;
+		} finally {
+			originalKey.release();
 		}
 	}
 
-	static byte[] firstRangeKey(byte[] prefixKey, int prefixLength, int suffixLength, int extLength) {
-		return zeroFillKeySuffixAndExt(prefixKey, prefixLength, suffixLength, extLength);
+	static ByteBuf firstRangeKey(ByteBufAllocator alloc, ByteBuf prefixKey, int prefixLength, int suffixLength, int extLength) {
+		return zeroFillKeySuffixAndExt(alloc, prefixKey, prefixLength, suffixLength, extLength);
 	}
 
-	static byte[] nextRangeKey(byte[] prefixKey, int prefixLength, int suffixLength, int extLength) {
-		byte[] nonIncremented = zeroFillKeySuffixAndExt(prefixKey, prefixLength, suffixLength, extLength);
-		return incrementPrefix(nonIncremented, prefixLength);
+	static ByteBuf nextRangeKey(ByteBufAllocator alloc, ByteBuf prefixKey, int prefixLength, int suffixLength, int extLength) {
+		try {
+			ByteBuf nonIncremented = zeroFillKeySuffixAndExt(alloc, prefixKey.retain(), prefixLength, suffixLength, extLength);
+			try {
+				return incrementPrefix(alloc, nonIncremented.retain(), prefixLength);
+			} finally {
+				nonIncremented.release();
+			}
+		} finally {
+			prefixKey.release();
+		}
 	}
 
-	protected static byte[] zeroFillKeySuffixAndExt(byte[] prefixKey, int prefixLength, int suffixLength, int extLength) {
-		assert prefixKey.length == prefixLength;
+	protected static ByteBuf zeroFillKeySuffixAndExt(ByteBufAllocator alloc, ByteBuf prefixKey, int prefixLength, int suffixLength, int extLength) {
+		try {
+			assert prefixKey.readableBytes() == prefixLength;
+			assert suffixLength > 0;
+			assert extLength >= 0;
+			if (!prefixKey.isDirect()) {
+				throw new IllegalArgumentException("Prefix key must be a direct buffer");
+			}
+			assert prefixKey.nioBuffer().isDirect();
+			ByteBuf zeroSuffixAndExt = alloc.directBuffer(suffixLength + extLength, suffixLength + extLength);
+			try {
+				assert zeroSuffixAndExt.isDirect();
+				assert zeroSuffixAndExt.nioBuffer().isDirect();
+				zeroSuffixAndExt.writeZero(suffixLength + extLength);
+				ByteBuf result = LLUtils.directCompositeBuffer(alloc, prefixKey.retain(), zeroSuffixAndExt.retain());
+				assert result.isDirect();
+				assert result.nioBuffer().isDirect();
+				return result;
+			} finally {
+				zeroSuffixAndExt.release();
+			}
+		} finally {
+			prefixKey.release();
+		}
+	}
+
+	static ByteBuf firstRangeKey(
+			ByteBufAllocator alloc,
+			ByteBuf prefixKey,
+			ByteBuf suffixKey,
+			int prefixLength,
+			int suffixLength,
+			int extLength) {
+		return zeroFillKeyExt(alloc, prefixKey, suffixKey, prefixLength, suffixLength, extLength);
+	}
+
+	static ByteBuf nextRangeKey(
+			ByteBufAllocator alloc,
+			ByteBuf prefixKey,
+			ByteBuf suffixKey,
+			int prefixLength,
+			int suffixLength,
+			int extLength) {
+		try {
+			ByteBuf nonIncremented = zeroFillKeyExt(alloc,
+					prefixKey.retain(),
+					suffixKey.retain(),
+					prefixLength,
+					suffixLength,
+					extLength
+			);
+			try {
+				return incrementPrefix(alloc, nonIncremented.retain(), prefixLength + suffixLength);
+			} finally {
+				nonIncremented.release();
+			}
+		} finally {
+			prefixKey.release();
+			suffixKey.release();
+		}
+	}
+
+	protected static ByteBuf zeroFillKeyExt(
+			ByteBufAllocator alloc,
+			ByteBuf prefixKey,
+			ByteBuf suffixKey,
+			int prefixLength,
+			int suffixLength,
+			int extLength) {
+		assert prefixKey.readableBytes() == prefixLength;
+		assert suffixKey.readableBytes() == suffixLength;
 		assert suffixLength > 0;
 		assert extLength >= 0;
-		byte[] result = Arrays.copyOf(prefixKey, prefixLength + suffixLength + extLength);
-		Arrays.fill(result, prefixLength, result.length, (byte) 0);
-		return result;
-	}
-
-	static byte[] firstRangeKey(byte[] prefixKey,
-			byte[] suffixKey,
-			int prefixLength,
-			int suffixLength,
-			int extLength) {
-		return zeroFillKeyExt(prefixKey, suffixKey, prefixLength, suffixLength, extLength);
-	}
-
-	static byte[] nextRangeKey(byte[] prefixKey,
-			byte[] suffixKey,
-			int prefixLength,
-			int suffixLength,
-			int extLength) {
-		byte[] nonIncremented = zeroFillKeyExt(prefixKey, suffixKey, prefixLength, suffixLength, extLength);
-		return incrementPrefix(nonIncremented, prefixLength + suffixLength);
-	}
-
-	protected static byte[] zeroFillKeyExt(byte[] prefixKey,
-			byte[] suffixKey,
-			int prefixLength,
-			int suffixLength,
-			int extLength) {
-		assert prefixKey.length == prefixLength;
-		assert suffixKey.length == suffixLength;
-		assert suffixLength > 0;
-		assert extLength >= 0;
-		byte[] result = Arrays.copyOf(prefixKey, prefixLength + suffixLength + extLength);
-		System.arraycopy(suffixKey, 0, result, prefixLength, suffixLength);
-		Arrays.fill(result, prefixLength + suffixLength, result.length, (byte) 0);
+		var result = LLUtils.directCompositeBuffer(alloc, prefixKey, suffixKey, alloc.buffer(extLength, extLength).writeZero(extLength));
+		assert result.readableBytes() == prefixLength + suffixLength + extLength;
 		return result;
 	}
 
@@ -104,41 +183,73 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 	 */
 	@Deprecated
 	public static <T, U> DatabaseMapDictionaryDeep<T, U, DatabaseStageEntry<U>> simple(LLDictionary dictionary,
-			SerializerFixedBinaryLength<T, byte[]> keySerializer,
+			SerializerFixedBinaryLength<T, ByteBuf> keySerializer,
 			SubStageGetterSingle<U> subStageGetter) {
 		return new DatabaseMapDictionaryDeep<>(dictionary, EMPTY_BYTES, keySerializer, subStageGetter, 0);
 	}
 
 	public static <T, U, US extends DatabaseStage<U>> DatabaseMapDictionaryDeep<T, U, US> deepTail(LLDictionary dictionary,
-			SerializerFixedBinaryLength<T, byte[]> keySerializer,
+			SerializerFixedBinaryLength<T, ByteBuf> keySerializer,
 			int keyExtLength,
 			SubStageGetter<U, US> subStageGetter) {
 		return new DatabaseMapDictionaryDeep<>(dictionary, EMPTY_BYTES, keySerializer, subStageGetter, keyExtLength);
 	}
 
 	public static <T, U, US extends DatabaseStage<U>> DatabaseMapDictionaryDeep<T, U, US> deepIntermediate(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer,
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer,
 			SubStageGetter<U, US> subStageGetter,
 			int keyExtLength) {
 		return new DatabaseMapDictionaryDeep<>(dictionary, prefixKey, keySuffixSerializer, subStageGetter, keyExtLength);
 	}
 
 	protected DatabaseMapDictionaryDeep(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer,
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer,
 			SubStageGetter<U, US> subStageGetter,
 			int keyExtLength) {
-		this.dictionary = dictionary;
-		this.subStageGetter = subStageGetter;
-		this.keySuffixSerializer = keySuffixSerializer;
-		this.keyPrefix = prefixKey;
-		this.keySuffixLength = keySuffixSerializer.getSerializedBinaryLength();
-		this.keyExtLength = keyExtLength;
-		byte[] firstKey = firstRangeKey(keyPrefix, keyPrefix.length, keySuffixLength, keyExtLength);
-		byte[] nextRangeKey = nextRangeKey(keyPrefix, keyPrefix.length, keySuffixLength, keyExtLength);
-		this.range = keyPrefix.length == 0 ? LLRange.all() : LLRange.of(firstKey, nextRangeKey);
-		assert subStageKeysConsistency(keyPrefix.length + keySuffixLength + keyExtLength);
+		try {
+			this.dictionary = dictionary;
+			this.alloc = dictionary.getAllocator();
+			this.subStageGetter = subStageGetter;
+			this.keySuffixSerializer = keySuffixSerializer;
+			this.keyPrefix = wrappedUnmodifiableBuffer(prefixKey).retain();
+			this.keyPrefixLength = keyPrefix.readableBytes();
+			this.keySuffixLength = keySuffixSerializer.getSerializedBinaryLength();
+			this.keyExtLength = keyExtLength;
+			if (!keyPrefix.isDirect()) {
+				throw new IllegalArgumentException("KeyPrefix must be a direct buffer");
+			}
+			assert keyPrefix.isDirect();
+			ByteBuf firstKey = wrappedUnmodifiableBuffer(firstRangeKey(alloc,
+					keyPrefix.retain(),
+					keyPrefixLength,
+					keySuffixLength,
+					keyExtLength
+			));
+			ByteBuf nextRangeKey = wrappedUnmodifiableBuffer(nextRangeKey(alloc,
+					keyPrefix.retain(),
+					keyPrefixLength,
+					keySuffixLength,
+					keyExtLength
+			));
+			try {
+				assert keyPrefixLength == 0 || !LLUtils.equals(firstKey, nextRangeKey);
+				assert firstKey.isDirect();
+				assert nextRangeKey.isDirect();
+				assert firstKey.nioBuffer().isDirect();
+				assert nextRangeKey.nioBuffer().isDirect();
+				this.range = keyPrefixLength == 0 ? LLRange.all() : LLRange.of(firstKey.retain(), nextRangeKey.retain());
+				assert range == null || !range.hasMin() || range.getMin().isDirect();
+				assert range == null || !range.hasMax() || range.getMax().isDirect();
+				assert subStageKeysConsistency(keyPrefixLength + keySuffixLength + keyExtLength);
+			} finally {
+				firstKey.release();
+				nextRangeKey.release();
+			}
+		} finally {
+			prefixKey.release();
+		}
 	}
 
 	@SuppressWarnings("unused")
@@ -159,26 +270,33 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 	/**
 	 * Keep only suffix and ext
 	 */
-	protected byte[] stripPrefix(byte[] key) {
-		return Arrays.copyOfRange(key, this.keyPrefix.length, key.length);
+	protected ByteBuf stripPrefix(ByteBuf key) {
+		return key.slice(this.keyPrefixLength, key.readableBytes() - this.keyPrefixLength);
 	}
 
 	/**
 	 * Remove ext from full key
 	 */
-	protected byte[] removeExtFromFullKey(byte[] key) {
-		return Arrays.copyOf(key, keyPrefix.length + keySuffixLength);
+	protected ByteBuf removeExtFromFullKey(ByteBuf key) {
+		try {
+			return key.slice(key.readerIndex(), keyPrefixLength + keySuffixLength).retain();
+		} finally {
+			key.release();
+		}
 	}
 
 	/**
 	 * Add prefix to suffix
 	 */
-	protected byte[] toKeyWithoutExt(byte[] suffixKey) {
-		assert suffixKey.length == keySuffixLength;
-		byte[] result = Arrays.copyOf(keyPrefix, keyPrefix.length + keySuffixLength);
-		System.arraycopy(suffixKey, 0, result, keyPrefix.length, keySuffixLength);
-		assert result.length == keyPrefix.length + keySuffixLength;
-		return result;
+	protected ByteBuf toKeyWithoutExt(ByteBuf suffixKey) {
+		try {
+			assert suffixKey.readableBytes() == keySuffixLength;
+			ByteBuf result = LLUtils.directCompositeBuffer(alloc, keyPrefix.retain(), suffixKey.retain());
+			assert result.readableBytes() == keyPrefixLength + keySuffixLength;
+			return result;
+		} finally {
+			suffixKey.release();
+		}
 	}
 
 	protected LLSnapshot resolveSnapshot(@Nullable CompositeSnapshot snapshot) {
@@ -189,71 +307,89 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 		}
 	}
 
-	protected LLRange toExtRange(byte[] keySuffix) {
-		byte[] first = firstRangeKey(keyPrefix, keySuffix, keyPrefix.length, keySuffixLength, keyExtLength);
-		byte[] end = nextRangeKey(keyPrefix, keySuffix, keyPrefix.length, keySuffixLength, keyExtLength);
-		return LLRange.of(first, end);
+	protected LLRange toExtRange(ByteBuf keySuffix) {
+		try {
+			ByteBuf first = firstRangeKey(alloc,
+					keyPrefix.retain(),
+					keySuffix.retain(),
+					keyPrefixLength,
+					keySuffixLength,
+					keyExtLength
+			);
+			ByteBuf end = nextRangeKey(alloc,
+					keyPrefix.retain(),
+					keySuffix.retain(),
+					keyPrefixLength,
+					keySuffixLength,
+					keyExtLength
+			);
+			return LLRange.of(first, end);
+		} finally {
+			keySuffix.release();
+		}
 	}
 
 	@Override
 	public Mono<Long> leavesCount(@Nullable CompositeSnapshot snapshot, boolean fast) {
-		return dictionary.sizeRange(resolveSnapshot(snapshot), range, fast);
+		return dictionary.sizeRange(resolveSnapshot(snapshot), range.retain(), fast);
 	}
 
 	@Override
 	public Mono<Boolean> isEmpty(@Nullable CompositeSnapshot snapshot) {
-		return dictionary.isRangeEmpty(resolveSnapshot(snapshot), range);
+		return dictionary.isRangeEmpty(resolveSnapshot(snapshot), range.retain());
 	}
 
 	@Override
 	public Mono<US> at(@Nullable CompositeSnapshot snapshot, T keySuffix) {
-		byte[] keySuffixData = serializeSuffix(keySuffix);
-		Flux<byte[]> keyFlux;
+		ByteBuf keySuffixData = serializeSuffix(keySuffix);
+		Flux<ByteBuf> keyFlux;
 		if (LLLocalDictionary.DEBUG_PREFIXES_WHEN_ASSERTIONS_ARE_ENABLED && this.subStageGetter.needsDebuggingKeyFlux()) {
-			keyFlux = this.dictionary.getRangeKeys(resolveSnapshot(snapshot), toExtRange(keySuffixData));
+			keyFlux = this.dictionary.getRangeKeys(resolveSnapshot(snapshot), toExtRange(keySuffixData.retain()));
 		} else {
 			keyFlux = Flux.empty();
 		}
 		return this.subStageGetter
-				.subStage(dictionary,
-						snapshot,
-						toKeyWithoutExt(keySuffixData),
-						keyFlux
-				);
+				.subStage(dictionary, snapshot, toKeyWithoutExt(keySuffixData.retain()), keyFlux)
+				.doFinally(s -> keySuffixData.release());
 	}
 
 	@Override
 	public Flux<Entry<T, US>> getAllStages(@Nullable CompositeSnapshot snapshot) {
 		if (LLLocalDictionary.DEBUG_PREFIXES_WHEN_ASSERTIONS_ARE_ENABLED && this.subStageGetter.needsDebuggingKeyFlux()) {
 			return dictionary
-					.getRangeKeysGrouped(resolveSnapshot(snapshot), range, keyPrefix.length + keySuffixLength)
+					.getRangeKeysGrouped(resolveSnapshot(snapshot), range.retain(), keyPrefixLength + keySuffixLength)
 					.flatMapSequential(rangeKeys -> {
 						assert this.subStageGetter.isMultiKey() || rangeKeys.size() == 1;
-						byte[] groupKeyWithExt = rangeKeys.get(0);
-						byte[] groupKeyWithoutExt = removeExtFromFullKey(groupKeyWithExt);
-						byte[] groupSuffix = this.stripPrefix(groupKeyWithoutExt);
-						assert subStageKeysConsistency(groupKeyWithExt.length);
+						ByteBuf groupKeyWithExt = rangeKeys.get(0).retain();
+						ByteBuf groupKeyWithoutExt = removeExtFromFullKey(groupKeyWithExt.retain());
+						ByteBuf groupSuffix = this.stripPrefix(groupKeyWithoutExt.retain());
+						assert subStageKeysConsistency(groupKeyWithExt.readableBytes());
 						return this.subStageGetter
 								.subStage(dictionary,
 										snapshot,
 										groupKeyWithoutExt,
 										Flux.fromIterable(rangeKeys)
 								)
-								.map(us -> Map.entry(this.deserializeSuffix(groupSuffix), us));
+								.map(us -> Map.entry(this.deserializeSuffix(wrappedUnmodifiableBuffer(groupSuffix.retain())), us))
+								.doFinally(s -> {
+									groupSuffix.release();
+									groupKeyWithoutExt.release();
+									groupKeyWithExt.release();
+								});
 					});
 		} else {
 			return dictionary
-					.getRangeKeyPrefixes(resolveSnapshot(snapshot), range, keyPrefix.length + keySuffixLength)
+					.getRangeKeyPrefixes(resolveSnapshot(snapshot), range, keyPrefixLength + keySuffixLength)
 					.flatMapSequential(groupKeyWithoutExt -> {
-						byte[] groupSuffix = this.stripPrefix(groupKeyWithoutExt);
-						assert subStageKeysConsistency(groupKeyWithoutExt.length + keyExtLength);
+						ByteBuf groupSuffix = this.stripPrefix(groupKeyWithoutExt);
+						assert subStageKeysConsistency(groupKeyWithoutExt.readableBytes() + keyExtLength);
 						return this.subStageGetter
 								.subStage(dictionary,
 										snapshot,
 										groupKeyWithoutExt,
 										Flux.empty()
 								)
-								.map(us -> Map.entry(this.deserializeSuffix(groupSuffix), us));
+								.map(us -> Map.entry(this.deserializeSuffix(wrappedUnmodifiableBuffer(groupSuffix)), us));
 					});
 		}
 	}
@@ -261,10 +397,10 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 	private boolean subStageKeysConsistency(int totalKeyLength) {
 		if (subStageGetter instanceof SubStageGetterMapDeep) {
 			return totalKeyLength
-					== keyPrefix.length + keySuffixLength + ((SubStageGetterMapDeep<?, ?, ?>) subStageGetter).getKeyBinaryLength();
+					== keyPrefixLength + keySuffixLength + ((SubStageGetterMapDeep<?, ?, ?>) subStageGetter).getKeyBinaryLength();
 		} else if (subStageGetter instanceof SubStageGetterMap) {
 			return totalKeyLength
-					== keyPrefix.length + keySuffixLength + ((SubStageGetterMap<?, ?>) subStageGetter).getKeyBinaryLength();
+					== keyPrefixLength + keySuffixLength + ((SubStageGetterMap<?, ?>) subStageGetter).getKeyBinaryLength();
 		} else {
 			return true;
 		}
@@ -287,25 +423,37 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 					.clear();
 		} else if (range.isSingle()) {
 			return dictionary
-					.remove(range.getSingle(), LLDictionaryResultType.VOID)
+					.remove(range.getSingle().retain(), LLDictionaryResultType.VOID)
 					.then();
 		} else {
 			return dictionary
-					.setRange(range, Flux.empty(), false)
+					.setRange(range.retain(), Flux.empty(), false)
 					.then();
 		}
 	}
 
 	//todo: temporary wrapper. convert the whole class to buffers
-	protected T deserializeSuffix(byte[] keySuffix) {
-		assert suffixKeyConsistency(keySuffix.length);
+	protected T deserializeSuffix(ByteBuf keySuffix) {
+		assert suffixKeyConsistency(keySuffix.readableBytes());
 		return keySuffixSerializer.deserialize(keySuffix);
 	}
 
 	//todo: temporary wrapper. convert the whole class to buffers
-	protected byte[] serializeSuffix(T keySuffix) {
-		byte[] suffixData = keySuffixSerializer.serialize(keySuffix);
-		assert suffixKeyConsistency(suffixData.length);
+	protected ByteBuf serializeSuffix(T keySuffix) {
+		ByteBuf suffixData = keySuffixSerializer.serialize(keySuffix);
+		assert suffixKeyConsistency(suffixData.readableBytes());
 		return suffixData;
 	}
+
+	@Override
+	protected void finalize() throws Throwable {
+		super.finalize();
+		range.release();
+	}
+
+	@Override
+	public void release() {
+		this.range.release();
+		this.keyPrefix.release();
+	}
 }

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

@@ -2,18 +2,18 @@ package it.cavallium.dbengine.database.collections;
 
 import static it.cavallium.dbengine.database.collections.DatabaseMapDictionaryDeep.EMPTY_BYTES;
 
-import com.google.common.primitives.Ints;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.LLUtils;
 import it.cavallium.dbengine.database.collections.Joiner.ValueGetter;
 import it.cavallium.dbengine.database.collections.JoinerBlocking.ValueGetterBlocking;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -23,19 +23,21 @@ import reactor.core.publisher.Mono;
 @SuppressWarnings("unused")
 public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T, U, DatabaseStageEntry<U>> {
 
+	private final ByteBufAllocator alloc;
 	private final DatabaseMapDictionary<TH, Entry<T, U>> subDictionary;
 	private final Function<T, TH> keySuffixHashFunction;
 	private final Function<T, ValueMapper<T, U>> valueMapper;
 
 	protected DatabaseMapDictionaryHashed(LLDictionary dictionary,
-			byte[] prefixKey,
-			Serializer<T, byte[]> keySuffixSerializer,
-			Serializer<U, byte[]> valueSerializer,
+			ByteBuf prefixKey,
+			Serializer<T, ByteBuf> keySuffixSerializer,
+			Serializer<U, ByteBuf> valueSerializer,
 			Function<T, TH> keySuffixHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keySuffixHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keySuffixHashSerializer) {
 		ValueWithHashSerializer<T, U> valueWithHashSerializer = new ValueWithHashSerializer<>(keySuffixSerializer,
 				valueSerializer
 		);
+		this.alloc = dictionary.getAllocator();
 		this.valueMapper = ValueMapper::new;
 		this.subDictionary = DatabaseMapDictionary.tail(dictionary,
 				prefixKey,
@@ -44,40 +46,35 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 		this.keySuffixHashFunction = keySuffixHashFunction;
 	}
 
-	private static class ValueWithHashSerializer<T, U> implements Serializer<Entry<T, U>, byte[]> {
+	private class ValueWithHashSerializer<T, U> implements Serializer<Entry<T, U>, ByteBuf> {
 
-		private final Serializer<T, byte[]> keySuffixSerializer;
-		private final Serializer<U, byte[]> valueSerializer;
+		private final Serializer<T, ByteBuf> keySuffixSerializer;
+		private final Serializer<U, ByteBuf> valueSerializer;
 
-		private ValueWithHashSerializer(Serializer<T, byte[]> keySuffixSerializer, Serializer<U, byte[]> valueSerializer) {
+		private ValueWithHashSerializer(Serializer<T, ByteBuf> keySuffixSerializer, Serializer<U, ByteBuf> valueSerializer) {
 			this.keySuffixSerializer = keySuffixSerializer;
 			this.valueSerializer = valueSerializer;
 		}
 
 		@Override
-		public @NotNull Entry<T, U> deserialize(byte @NotNull [] serialized) {
-			int keySuffixLength = Ints.fromBytes(serialized[0], serialized[1], serialized[2], serialized[3]);
-			T keySuffix = keySuffixSerializer.deserialize(Arrays.copyOfRange(serialized,
-					Integer.BYTES,
-					Integer.BYTES + keySuffixLength
-			));
-			U value = valueSerializer.deserialize(Arrays.copyOfRange(serialized,
-					Integer.BYTES + keySuffixLength,
-					serialized.length
-			));
-			return Map.entry(keySuffix, value);
+		public @NotNull Entry<T, U> deserialize(@NotNull ByteBuf serialized) {
+			try {
+				int keySuffixLength = serialized.readInt();
+				T keySuffix = keySuffixSerializer.deserialize(serialized.retainedSlice(serialized.readerIndex(), keySuffixLength));
+				U value = valueSerializer.deserialize(serialized.retain());
+				return Map.entry(keySuffix, value);
+			} finally {
+				serialized.release();
+			}
 		}
 
 		@Override
-		public byte @NotNull [] serialize(@NotNull Entry<T, U> deserialized) {
-			byte[] keySuffix = keySuffixSerializer.serialize(deserialized.getKey());
-			byte[] value = valueSerializer.serialize(deserialized.getValue());
-			byte[] result = new byte[Integer.BYTES + keySuffix.length + value.length];
-			byte[] keySuffixLen = Ints.toByteArray(keySuffix.length);
-			System.arraycopy(keySuffixLen, 0, result, 0, Integer.BYTES);
-			System.arraycopy(keySuffix, 0, result, Integer.BYTES, keySuffix.length);
-			System.arraycopy(value, 0, result, Integer.BYTES + keySuffix.length, value.length);
-			return result;
+		public @NotNull ByteBuf serialize(@NotNull Entry<T, U> deserialized) {
+			ByteBuf keySuffix = keySuffixSerializer.serialize(deserialized.getKey());
+			ByteBuf value = valueSerializer.serialize(deserialized.getValue());
+			ByteBuf keySuffixLen = alloc.buffer(Integer.BYTES, Integer.BYTES);
+			keySuffixLen.writeInt(keySuffix.readableBytes());
+			return LLUtils.directCompositeBuffer(alloc, keySuffixLen, keySuffix, value);
 		}
 	}
 
@@ -101,10 +98,10 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	public static <T, U, UH> DatabaseMapDictionaryHashed<T, U, UH> simple(LLDictionary dictionary,
-			Serializer<T, byte[]> keySerializer,
-			Serializer<U, byte[]> valueSerializer,
+			Serializer<T, ByteBuf> keySerializer,
+			Serializer<U, ByteBuf> valueSerializer,
 			Function<T, UH> keyHashFunction,
-			SerializerFixedBinaryLength<UH, byte[]> keyHashSerializer) {
+			SerializerFixedBinaryLength<UH, ByteBuf> keyHashSerializer) {
 		return new DatabaseMapDictionaryHashed<>(dictionary,
 				EMPTY_BYTES,
 				keySerializer,
@@ -115,11 +112,11 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	public static <T, U, UH> DatabaseMapDictionaryHashed<T, U, UH> tail(LLDictionary dictionary,
-			byte[] prefixKey,
-			Serializer<T, byte[]> keySuffixSerializer,
-			Serializer<U, byte[]> valueSerializer,
+			ByteBuf prefixKey,
+			Serializer<T, ByteBuf> keySuffixSerializer,
+			Serializer<U, ByteBuf> valueSerializer,
 			Function<T, UH> keySuffixHashFunction,
-			SerializerFixedBinaryLength<UH, byte[]> keySuffixHashSerializer) {
+			SerializerFixedBinaryLength<UH, ByteBuf> keySuffixHashSerializer) {
 		return new DatabaseMapDictionaryHashed<>(dictionary,
 				prefixKey,
 				keySuffixSerializer,
@@ -157,13 +154,20 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	@Override
-	public Mono<Boolean> setAndGetStatus(Map<T, U> map) {
-		return Mono.fromSupplier(() -> this.serializeMap(map)).flatMap(subDictionary::setAndGetStatus);
+	public Mono<Boolean> setAndGetChanged(Map<T, U> map) {
+		return Mono.fromSupplier(() -> this.serializeMap(map)).flatMap(subDictionary::setAndGetChanged).single();
 	}
 
 	@Override
-	public Mono<Boolean> update(Function<Optional<Map<T, U>>, Optional<Map<T, U>>> updater) {
-		return subDictionary.update(old -> updater.apply(old.map(this::deserializeMap)).map(this::serializeMap));
+	public Mono<Boolean> update(Function<@Nullable Map<T, U>, @Nullable Map<T, U>> updater) {
+		return subDictionary.update(old -> {
+			var result = updater.apply(old == null ? null : this.deserializeMap(old));
+			if (result == null) {
+				return null;
+			} else {
+				return this.serializeMap(result);
+			}
+		});
 	}
 
 	@Override
@@ -186,6 +190,11 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 		return this;
 	}
 
+	@Override
+	public void release() {
+		this.subDictionary.release();
+	}
+
 	@Override
 	public Mono<DatabaseStageEntry<U>> at(@Nullable CompositeSnapshot snapshot, T key) {
 		return subDictionary
@@ -218,18 +227,27 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	@Override
-	public Mono<Boolean> updateValue(T key, boolean existsAlmostCertainly, Function<Optional<U>, Optional<U>> updater) {
-		return subDictionary.updateValue(keySuffixHashFunction.apply(key),
-				existsAlmostCertainly,
-				old -> updater.apply(old.map(Entry::getValue)).map(newV -> Map.entry(key, newV))
-		);
+	public Mono<Boolean> updateValue(T key, boolean existsAlmostCertainly, Function<@Nullable U, @Nullable U> updater) {
+		return subDictionary.updateValue(keySuffixHashFunction.apply(key), existsAlmostCertainly, old -> {
+			var result = updater.apply(old == null ? null : old.getValue());
+			if (result == null) {
+				return null;
+			} else {
+				return Map.entry(key, result);
+			}
+		});
 	}
 
 	@Override
-	public Mono<Boolean> updateValue(T key, Function<Optional<U>, Optional<U>> updater) {
-		return subDictionary.updateValue(keySuffixHashFunction.apply(key),
-				old -> updater.apply(old.map(Entry::getValue)).map(newV -> Map.entry(key, newV))
-		);
+	public Mono<Boolean> updateValue(T key, Function<@Nullable U, @Nullable U> updater) {
+		return subDictionary.updateValue(keySuffixHashFunction.apply(key), old -> {
+			var result = updater.apply(old == null ? null : old.getValue());
+			if (result == null) {
+				return null;
+			} else {
+				return Map.entry(key, result);
+			}
+		});
 	}
 
 	@Override
@@ -346,10 +364,16 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	@Override
-	public Mono<Boolean> update(Function<Optional<Map<T, U>>, Optional<Map<T, U>>> updater,
+	public Mono<Boolean> update(Function<@Nullable Map<T, U>, @Nullable Map<T, U>> updater,
 			boolean existsAlmostCertainly) {
-		return subDictionary
-				.update(item -> updater.apply(item.map(this::deserializeMap)).map(this::serializeMap), existsAlmostCertainly);
+		return subDictionary.update(item -> {
+			var result = updater.apply(item == null ? null : this.deserializeMap(item));
+			if (result == null) {
+				return null;
+			} else {
+				return this.serializeMap(result);
+			}
+		}, existsAlmostCertainly);
 	}
 
 	@Override

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
@@ -14,19 +15,19 @@ import reactor.core.publisher.Mono;
 public class DatabaseSetDictionary<T> extends DatabaseMapDictionaryDeep<T, Nothing, DatabaseStageEntry<Nothing>> {
 
 	protected DatabaseSetDictionary(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer) {
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer) {
 		super(dictionary, prefixKey, keySuffixSerializer, DatabaseEmpty.createSubStageGetter(), 0);
 	}
 
 	public static <T> DatabaseSetDictionary<T> simple(LLDictionary dictionary,
-			SerializerFixedBinaryLength<T, byte[]> keySerializer) {
+			SerializerFixedBinaryLength<T, ByteBuf> keySerializer) {
 		return new DatabaseSetDictionary<>(dictionary, EMPTY_BYTES, keySerializer);
 	}
 
 	public static <T> DatabaseSetDictionary<T> tail(LLDictionary dictionary,
-			byte[] prefixKey,
-			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer) {
+			ByteBuf prefixKey,
+			SerializerFixedBinaryLength<T, ByteBuf> keySuffixSerializer) {
 		return new DatabaseSetDictionary<>(dictionary, prefixKey, keySuffixSerializer);
 	}
 

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

@@ -2,6 +2,7 @@ package it.cavallium.dbengine.database.collections;
 
 import static it.cavallium.dbengine.database.collections.DatabaseMapDictionaryDeep.EMPTY_BYTES;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
@@ -18,10 +19,10 @@ import reactor.core.publisher.Mono;
 public class DatabaseSetDictionaryHashed<T, TH> extends DatabaseMapDictionaryHashed<T, Nothing, TH> {
 
 	protected DatabaseSetDictionaryHashed(LLDictionary dictionary,
-			byte[] prefixKey,
-			Serializer<T, byte[]> keySuffixSerializer,
+			ByteBuf prefixKey,
+			Serializer<T, ByteBuf> keySuffixSerializer,
 			Function<T, TH> keySuffixHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keySuffixHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keySuffixHashSerializer) {
 		super(dictionary,
 				prefixKey,
 				keySuffixSerializer,
@@ -32,9 +33,9 @@ public class DatabaseSetDictionaryHashed<T, TH> extends DatabaseMapDictionaryHas
 	}
 
 	public static <T, TH> DatabaseSetDictionaryHashed<T, TH> simple(LLDictionary dictionary,
-			Serializer<T, byte[]> keySerializer,
+			Serializer<T, ByteBuf> keySerializer,
 			Function<T, TH> keyHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer) {
 		return new DatabaseSetDictionaryHashed<>(dictionary,
 				EMPTY_BYTES,
 				keySerializer,
@@ -44,10 +45,10 @@ public class DatabaseSetDictionaryHashed<T, TH> extends DatabaseMapDictionaryHas
 	}
 
 	public static <T, TH> DatabaseSetDictionaryHashed<T, TH> tail(LLDictionary dictionary,
-			byte[] prefixKey,
-			Serializer<T, byte[]> keySuffixSerializer,
+			ByteBuf prefixKey,
+			Serializer<T, ByteBuf> keySuffixSerializer,
 			Function<T, TH> keyHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer) {
 		return new DatabaseSetDictionaryHashed<>(dictionary,
 				prefixKey,
 				keySuffixSerializer,

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.LLDictionaryResultType;
@@ -10,15 +11,19 @@ import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Mono;
+import static io.netty.buffer.Unpooled.*;
 
 public class DatabaseSingle<U> implements DatabaseStageEntry<U> {
 
 	private final LLDictionary dictionary;
-	private final byte[] key;
-	private final Serializer<U, byte[]> serializer;
+	private final ByteBuf key;
+	private final Serializer<U, ByteBuf> serializer;
 
-	public DatabaseSingle(LLDictionary dictionary, byte[] key, Serializer<U, byte[]> serializer) {
+	public DatabaseSingle(LLDictionary dictionary, ByteBuf key, Serializer<U, ByteBuf> serializer) {
 		this.dictionary = dictionary;
+		if (!key.isDirect()) {
+			throw new IllegalArgumentException("Key must be direct");
+		}
 		this.key = key;
 		this.serializer = serializer;
 	}
@@ -33,47 +38,60 @@ public class DatabaseSingle<U> implements DatabaseStageEntry<U> {
 
 	@Override
 	public Mono<U> get(@Nullable CompositeSnapshot snapshot, boolean existsAlmostCertainly) {
-		return dictionary.get(resolveSnapshot(snapshot), key, existsAlmostCertainly).map(this::deserialize);
+		return dictionary.get(resolveSnapshot(snapshot), key.retain(), existsAlmostCertainly).map(this::deserialize);
 	}
 
 	@Override
 	public Mono<U> setAndGetPrevious(U value) {
-		return dictionary.put(key, serialize(value), LLDictionaryResultType.PREVIOUS_VALUE).map(this::deserialize);
+		ByteBuf valueByteBuf = serialize(value);
+		return dictionary
+				.put(key.retain(), valueByteBuf.retain(), LLDictionaryResultType.PREVIOUS_VALUE)
+				.map(this::deserialize)
+				.doFinally(s -> valueByteBuf.release());
 	}
 
 	@Override
-	public Mono<Boolean> update(Function<Optional<U>, Optional<U>> updater, boolean existsAlmostCertainly) {
-		return dictionary.update(key,
-				(oldValueSer) -> updater.apply(oldValueSer.map(this::deserialize)).map(this::serialize),
-				existsAlmostCertainly
-		);
+	public Mono<Boolean> update(Function<@Nullable U, @Nullable U> updater, boolean existsAlmostCertainly) {
+		return dictionary.update(key.retain(), (oldValueSer) -> {
+			var result = updater.apply(oldValueSer == null ? null : this.deserialize(oldValueSer));
+			if (result == null) {
+				return null;
+			} else {
+				return this.serialize(result);
+			}
+		}, existsAlmostCertainly);
 	}
 
 	@Override
 	public Mono<U> clearAndGetPrevious() {
-		return dictionary.remove(key, LLDictionaryResultType.PREVIOUS_VALUE).map(this::deserialize);
+		return dictionary.remove(key.retain(), LLDictionaryResultType.PREVIOUS_VALUE).map(this::deserialize);
 	}
 
 	@Override
 	public Mono<Long> leavesCount(@Nullable CompositeSnapshot snapshot, boolean fast) {
 		return dictionary
-				.isRangeEmpty(resolveSnapshot(snapshot), LLRange.single(key))
+				.isRangeEmpty(resolveSnapshot(snapshot), LLRange.single(key.retain()))
 				.map(empty -> empty ? 0L : 1L);
 	}
 
 	@Override
 	public Mono<Boolean> isEmpty(@Nullable CompositeSnapshot snapshot) {
 		return dictionary
-				.isRangeEmpty(resolveSnapshot(snapshot), LLRange.single(key));
+				.isRangeEmpty(resolveSnapshot(snapshot), LLRange.single(key.retain()));
 	}
 
 	//todo: temporary wrapper. convert the whole class to buffers
-	private U deserialize(byte[] bytes) {
+	private U deserialize(ByteBuf bytes) {
 		return serializer.deserialize(bytes);
 	}
 
 	//todo: temporary wrapper. convert the whole class to buffers
-	private byte[] serialize(U bytes) {
+	private ByteBuf serialize(U bytes) {
 		return serializer.serialize(bytes);
 	}
+
+	@Override
+	public void release() {
+		key.release();
+	}
 }

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

@@ -2,7 +2,6 @@ package it.cavallium.dbengine.database.collections;
 
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.serialization.Serializer;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Mono;
@@ -39,14 +38,20 @@ public class DatabaseSingleMapped<A, B> implements DatabaseStageEntry<A> {
 	}
 
 	@Override
-	public Mono<Boolean> setAndGetStatus(A value) {
-		return serializedSingle.setAndGetStatus(serialize(value));
+	public Mono<Boolean> setAndGetChanged(A value) {
+		return serializedSingle.setAndGetChanged(serialize(value)).single();
 	}
 
 	@Override
-	public Mono<Boolean> update(Function<Optional<A>, Optional<A>> updater, boolean existsAlmostCertainly) {
-		return serializedSingle
-				.update(oldValue -> updater.apply(oldValue.map(this::deserialize)).map(this::serialize), existsAlmostCertainly);
+	public Mono<Boolean> update(Function<@Nullable A, @Nullable A> updater, boolean existsAlmostCertainly) {
+		return serializedSingle.update(oldValue -> {
+			var result = updater.apply(oldValue == null ? null : this.deserialize(oldValue));
+			if (result == null) {
+				return null;
+			} else {
+				return this.serialize(result);
+			}
+		}, existsAlmostCertainly);
 	}
 
 	@Override
@@ -84,6 +89,11 @@ public class DatabaseSingleMapped<A, B> implements DatabaseStageEntry<A> {
 		return this;
 	}
 
+	@Override
+	public void release() {
+		serializedSingle.release();
+	}
+
 	//todo: temporary wrapper. convert the whole class to buffers
 	private A deserialize(B bytes) {
 		return serializer.deserialize(bytes);

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

@@ -2,7 +2,6 @@ package it.cavallium.dbengine.database.collections;
 
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Mono;
@@ -26,18 +25,18 @@ public interface DatabaseStage<T> extends DatabaseStageWithEntry<T> {
 	}
 
 	default Mono<Void> set(T value) {
-		return setAndGetStatus(value).then();
+		return setAndGetChanged(value).then();
 	}
 
 	Mono<T> setAndGetPrevious(T value);
 
-	default Mono<Boolean> setAndGetStatus(T value) {
-		return setAndGetPrevious(value).map(oldValue -> !Objects.equals(oldValue, value)).defaultIfEmpty(false);
+	default Mono<Boolean> setAndGetChanged(T value) {
+		return setAndGetPrevious(value).map(oldValue -> !Objects.equals(oldValue, value)).defaultIfEmpty(value != null);
 	}
 
-	Mono<Boolean> update(Function<Optional<T>, Optional<T>> updater, boolean existsAlmostCertainly);
+	Mono<Boolean> update(Function<@Nullable T, @Nullable T> updater, boolean existsAlmostCertainly);
 
-	default Mono<Boolean> update(Function<Optional<T>, Optional<T>> updater) {
+	default Mono<Boolean> update(Function<@Nullable T, @Nullable T> updater) {
 		return update(updater, false);
 	}
 
@@ -51,6 +50,8 @@ public interface DatabaseStage<T> extends DatabaseStageWithEntry<T> {
 		return clearAndGetPrevious().map(Objects::nonNull).defaultIfEmpty(false);
 	}
 
+	void release();
+
 	default Mono<Void> close() {
 		return Mono.empty();
 	}

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

@@ -6,7 +6,6 @@ import it.cavallium.dbengine.database.collections.JoinerBlocking.ValueGetterBloc
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.function.Function;
 import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Flux;
@@ -18,7 +17,7 @@ public interface DatabaseStageMap<T, U, US extends DatabaseStage<U>> extends Dat
 	Mono<US> at(@Nullable CompositeSnapshot snapshot, T key);
 
 	default Mono<U> getValue(@Nullable CompositeSnapshot snapshot, T key, boolean existsAlmostCertainly) {
-		return this.at(snapshot, key).flatMap(v -> v.get(snapshot, existsAlmostCertainly));
+		return this.at(snapshot, key).flatMap(v -> v.get(snapshot, existsAlmostCertainly).doFinally(s -> v.release()));
 	}
 
 	default Mono<U> getValue(@Nullable CompositeSnapshot snapshot, T key) {
@@ -30,23 +29,29 @@ public interface DatabaseStageMap<T, U, US extends DatabaseStage<U>> extends Dat
 	}
 
 	default Mono<Void> putValue(T key, U value) {
-		return at(null, key).single().flatMap(v -> v.set(value));
+		return at(null, key).single().flatMap(v -> v.set(value).doFinally(s -> v.release()));
 	}
 
-	default Mono<Boolean> updateValue(T key, boolean existsAlmostCertainly, Function<Optional<U>, Optional<U>> updater) {
-		return at(null, key).single().flatMap(v -> v.update(updater, existsAlmostCertainly));
+	default Mono<Boolean> updateValue(T key, boolean existsAlmostCertainly, Function<@Nullable U, @Nullable U> updater) {
+		return at(null, key).single().flatMap(v -> v.update(updater, existsAlmostCertainly).doFinally(s -> v.release()));
 	}
 
-	default Mono<Boolean> updateValue(T key, Function<Optional<U>, Optional<U>> updater) {
+	default Mono<Boolean> updateValue(T key, Function<@Nullable U, @Nullable U> updater) {
 		return updateValue(key, false, updater);
 	}
 
 	default Mono<U> putValueAndGetPrevious(T key, U value) {
-		return at(null, key).single().flatMap(v -> v.setAndGetPrevious(value));
+		return at(null, key).single().flatMap(v -> v.setAndGetPrevious(value).doFinally(s -> v.release()));
 	}
 
+	/**
+	 *
+	 * @param key
+	 * @param value
+	 * @return true if the key was associated with any value, false if the key didn't exist.
+	 */
 	default Mono<Boolean> putValueAndGetStatus(T key, U value) {
-		return at(null, key).single().flatMap(v -> v.setAndGetStatus(value));
+		return at(null, key).single().flatMap(v -> v.setAndGetChanged(value).doFinally(s -> v.release())).single();
 	}
 
 	default Mono<Void> remove(T key) {
@@ -54,7 +59,7 @@ public interface DatabaseStageMap<T, U, US extends DatabaseStage<U>> extends Dat
 	}
 
 	default Mono<U> removeAndGetPrevious(T key) {
-		return at(null, key).flatMap(DatabaseStage::clearAndGetPrevious);
+		return at(null, key).flatMap(v -> v.clearAndGetPrevious().doFinally(s -> v.release()));
 	}
 
 	default Mono<Boolean> removeAndGetStatus(T key) {
@@ -106,7 +111,7 @@ public interface DatabaseStageMap<T, U, US extends DatabaseStage<U>> extends Dat
 					.flatMap(entriesReplacer)
 					.flatMap(replacedEntry -> this
 							.at(null, replacedEntry.getKey())
-							.map(entry -> entry.set(replacedEntry.getValue())))
+							.map(v -> v.set(replacedEntry.getValue()).doFinally(s -> v.release())))
 					.then();
 		}
 	}
@@ -126,15 +131,23 @@ public interface DatabaseStageMap<T, U, US extends DatabaseStage<U>> extends Dat
 	}
 
 	@Override
-	default Mono<Boolean> update(Function<Optional<Map<T, U>>, Optional<Map<T, U>>> updater, boolean existsAlmostCertainly) {
+	default Mono<Boolean> update(Function<@Nullable Map<T, U>, @Nullable Map<T, U>> updater, boolean existsAlmostCertainly) {
 		return this
 				.getAllValues(null)
 				.collectMap(Entry::getKey, Entry::getValue, HashMap::new)
 				.single()
-				.map(v -> v.isEmpty() ? Optional.<Map<T, U>>empty() : Optional.of(v))
-				.map(updater)
-				.filter(Optional::isPresent)
-				.map(Optional::get)
+				.<Map<T, U>>handle((v, sink) -> {
+					if (v == null || v.isEmpty()) {
+						sink.complete();
+					} else {
+						var result = updater.apply(v);
+						if (result == null) {
+							sink.complete();
+						} else {
+							sink.next(result);
+						}
+					}
+				})
 				.flatMap(values -> this.setAllValues(Flux.fromIterable(values.entrySet())))
 				//todo: can be optimized by calculating the correct return value
 				.thenReturn(true);

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import org.jetbrains.annotations.Nullable;
@@ -10,8 +11,8 @@ public interface SubStageGetter<U, US extends DatabaseStage<U>> {
 
 	Mono<US> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux);
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux);
 
 	boolean isMultiKey();
 

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.serialization.Serializer;
@@ -23,15 +24,15 @@ public class SubStageGetterHashMap<T, U, TH> implements
 		assertsEnabled = assertsEnabledTmp;
 	}
 
-	private final Serializer<T, byte[]> keySerializer;
-	private final Serializer<U, byte[]> valueSerializer;
+	private final Serializer<T, ByteBuf> keySerializer;
+	private final Serializer<U, ByteBuf> valueSerializer;
 	private final Function<T, TH> keyHashFunction;
-	private final SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer;
+	private final SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer;
 
-	public SubStageGetterHashMap(Serializer<T, byte[]> keySerializer,
-			Serializer<U, byte[]> valueSerializer,
+	public SubStageGetterHashMap(Serializer<T, ByteBuf> keySerializer,
+			Serializer<U, ByteBuf> valueSerializer,
 			Function<T, TH> keyHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer) {
 		this.keySerializer = keySerializer;
 		this.valueSerializer = valueSerializer;
 		this.keyHashFunction = keyHashFunction;
@@ -41,8 +42,8 @@ public class SubStageGetterHashMap<T, U, TH> implements
 	@Override
 	public Mono<DatabaseMapDictionaryHashed<T, U, TH>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux) {
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux) {
 		Mono<DatabaseMapDictionaryHashed<T, U, TH>> result = Mono.just(DatabaseMapDictionaryHashed.tail(dictionary,
 				prefixKey,
 				keySerializer,
@@ -67,9 +68,9 @@ public class SubStageGetterHashMap<T, U, TH> implements
 		return assertsEnabled;
 	}
 
-	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+	private Mono<Void> checkKeyFluxConsistency(ByteBuf prefixKey, Flux<ByteBuf> keyFlux) {
 		return keyFlux.doOnNext(key -> {
-			assert key.length == prefixKey.length + getKeyHashBinaryLength();
+			assert key.readableBytes() == prefixKey.readableBytes() + getKeyHashBinaryLength();
 		}).then();
 	}
 

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
@@ -24,13 +25,13 @@ public class SubStageGetterHashSet<T, TH> implements
 		assertsEnabled = assertsEnabledTmp;
 	}
 
-	private final Serializer<T, byte[]> keySerializer;
+	private final Serializer<T, ByteBuf> keySerializer;
 	private final Function<T, TH> keyHashFunction;
-	private final SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer;
+	private final SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer;
 
-	public SubStageGetterHashSet(Serializer<T, byte[]> keySerializer,
+	public SubStageGetterHashSet(Serializer<T, ByteBuf> keySerializer,
 			Function<T, TH> keyHashFunction,
-			SerializerFixedBinaryLength<TH, byte[]> keyHashSerializer) {
+			SerializerFixedBinaryLength<TH, ByteBuf> keyHashSerializer) {
 		this.keySerializer = keySerializer;
 		this.keyHashFunction = keyHashFunction;
 		this.keyHashSerializer = keyHashSerializer;
@@ -39,8 +40,8 @@ public class SubStageGetterHashSet<T, TH> implements
 	@Override
 	public Mono<DatabaseSetDictionaryHashed<T, TH>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux) {
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux) {
 		Mono<DatabaseSetDictionaryHashed<T, TH>> result = Mono.just(DatabaseSetDictionaryHashed.tail(dictionary,
 				prefixKey,
 				keySerializer,
@@ -64,9 +65,9 @@ public class SubStageGetterHashSet<T, TH> implements
 		return assertsEnabled;
 	}
 
-	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+	private Mono<Void> checkKeyFluxConsistency(ByteBuf prefixKey, Flux<ByteBuf> keyFlux) {
 		return keyFlux.doOnNext(key -> {
-			assert key.length == prefixKey.length + getKeyHashBinaryLength();
+			assert key.readableBytes() == prefixKey.readableBytes() + getKeyHashBinaryLength();
 		}).then();
 	}
 

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.serialization.Serializer;
@@ -20,11 +21,11 @@ public class SubStageGetterMap<T, U> implements SubStageGetter<Map<T, U>, Databa
 		assertsEnabled = assertsEnabledTmp;
 	}
 
-	private final SerializerFixedBinaryLength<T, byte[]> keySerializer;
-	private final Serializer<U, byte[]> valueSerializer;
+	private final SerializerFixedBinaryLength<T, ByteBuf> keySerializer;
+	private final Serializer<U, ByteBuf> valueSerializer;
 
-	public SubStageGetterMap(SerializerFixedBinaryLength<T, byte[]> keySerializer,
-			Serializer<U, byte[]> valueSerializer) {
+	public SubStageGetterMap(SerializerFixedBinaryLength<T, ByteBuf> keySerializer,
+			Serializer<U, ByteBuf> valueSerializer) {
 		this.keySerializer = keySerializer;
 		this.valueSerializer = valueSerializer;
 	}
@@ -32,8 +33,8 @@ public class SubStageGetterMap<T, U> implements SubStageGetter<Map<T, U>, Databa
 	@Override
 	public Mono<DatabaseMapDictionary<T, U>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux) {
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux) {
 		Mono<DatabaseMapDictionary<T, U>> result = Mono.just(DatabaseMapDictionary.tail(dictionary, prefixKey, keySerializer,
 				valueSerializer
 		));
@@ -54,9 +55,9 @@ public class SubStageGetterMap<T, U> implements SubStageGetter<Map<T, U>, Databa
 		return assertsEnabled;
 	}
 
-	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+	private Mono<Void> checkKeyFluxConsistency(ByteBuf prefixKey, Flux<ByteBuf> keyFlux) {
 		return keyFlux.doOnNext(key -> {
-			assert key.length == prefixKey.length + getKeyBinaryLength();
+			assert key.readableBytes() == prefixKey.readableBytes() + getKeyBinaryLength();
 		}).then();
 	}
 

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
@@ -20,11 +21,11 @@ public class SubStageGetterMapDeep<T, U, US extends DatabaseStage<U>> implements
 	}
 
 	private final SubStageGetter<U, US> subStageGetter;
-	private final SerializerFixedBinaryLength<T, byte[]> keySerializer;
+	private final SerializerFixedBinaryLength<T, ByteBuf> keySerializer;
 	private final int keyExtLength;
 
 	public SubStageGetterMapDeep(SubStageGetter<U, US> subStageGetter,
-			SerializerFixedBinaryLength<T, byte[]> keySerializer,
+			SerializerFixedBinaryLength<T, ByteBuf> keySerializer,
 			int keyExtLength) {
 		this.subStageGetter = subStageGetter;
 		this.keySerializer = keySerializer;
@@ -46,8 +47,8 @@ public class SubStageGetterMapDeep<T, U, US extends DatabaseStage<U>> implements
 	@Override
 	public Mono<DatabaseMapDictionaryDeep<T, U, US>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux) {
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux) {
 		Mono<DatabaseMapDictionaryDeep<T, U, US>> result = Mono.just(DatabaseMapDictionaryDeep.deepIntermediate(dictionary,
 				prefixKey,
 				keySerializer,
@@ -71,9 +72,9 @@ public class SubStageGetterMapDeep<T, U, US extends DatabaseStage<U>> implements
 		return assertsEnabled;
 	}
 
-	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+	private Mono<Void> checkKeyFluxConsistency(ByteBuf prefixKey, Flux<ByteBuf> keyFlux) {
 		return keyFlux.doOnNext(key -> {
-			assert key.length == prefixKey.length + getKeyBinaryLength();
+			assert key.readableBytes() == prefixKey.readableBytes() + getKeyBinaryLength();
 		}).then();
 	}
 

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

@@ -1,5 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
@@ -20,22 +21,27 @@ public class SubStageGetterSet<T> implements SubStageGetter<Map<T, Nothing>, Dat
 		assertsEnabled = assertsEnabledTmp;
 	}
 
-	private final SerializerFixedBinaryLength<T, byte[]> keySerializer;
+	private final SerializerFixedBinaryLength<T, ByteBuf> keySerializer;
 
-	public SubStageGetterSet(SerializerFixedBinaryLength<T, byte[]> keySerializer) {
+	public SubStageGetterSet(SerializerFixedBinaryLength<T, ByteBuf> keySerializer) {
 		this.keySerializer = keySerializer;
 	}
 
 	@Override
 	public Mono<DatabaseSetDictionary<T>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] prefixKey,
-			Flux<byte[]> debuggingKeyFlux) {
-		Mono<DatabaseSetDictionary<T>> result = Mono.just(DatabaseSetDictionary.tail(dictionary, prefixKey, keySerializer));
-		if (assertsEnabled) {
-			return checkKeyFluxConsistency(prefixKey, debuggingKeyFlux).then(result);
-		} else {
-			return result;
+			ByteBuf prefixKey,
+			Flux<ByteBuf> debuggingKeyFlux) {
+		try {
+			Mono<DatabaseSetDictionary<T>> result = Mono
+					.fromSupplier(() -> DatabaseSetDictionary.tail(dictionary, prefixKey.retain(), keySerializer));
+			if (assertsEnabled) {
+				return checkKeyFluxConsistency(prefixKey.retain(), debuggingKeyFlux).then(result);
+			} else {
+				return result;
+			}
+		} finally {
+			prefixKey.release();
 		}
 	}
 
@@ -49,10 +55,10 @@ public class SubStageGetterSet<T> implements SubStageGetter<Map<T, Nothing>, Dat
 		return assertsEnabled;
 	}
 
-	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+	private Mono<Void> checkKeyFluxConsistency(ByteBuf prefixKey, Flux<ByteBuf> keyFlux) {
 		return keyFlux.doOnNext(key -> {
-			assert key.length == prefixKey.length + getKeyBinaryLength();
-		}).then();
+			assert key.readableBytes() == prefixKey.readableBytes() + getKeyBinaryLength();
+		}).doFinally(s -> prefixKey.release()).then();
 	}
 
 	public int getKeyBinaryLength() {

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

@@ -1,7 +1,9 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.LLUtils;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import java.util.Arrays;
 import org.jetbrains.annotations.Nullable;
@@ -19,22 +21,22 @@ public class SubStageGetterSingle<T> implements SubStageGetter<T, DatabaseStageE
 		assertsEnabled = assertsEnabledTmp;
 	}
 
-	private final Serializer<T, byte[]> serializer;
+	private final Serializer<T, ByteBuf> serializer;
 
-	public SubStageGetterSingle(Serializer<T, byte[]> serializer) {
+	public SubStageGetterSingle(Serializer<T, ByteBuf> serializer) {
 		this.serializer = serializer;
 	}
 
 	@Override
 	public Mono<DatabaseStageEntry<T>> subStage(LLDictionary dictionary,
 			@Nullable CompositeSnapshot snapshot,
-			byte[] keyPrefix,
-			Flux<byte[]> debuggingKeyFlux) {
+			ByteBuf keyPrefix,
+			Flux<ByteBuf> debuggingKeyFlux) {
 		return debuggingKeyFlux
 				.singleOrEmpty()
 				.flatMap(key -> Mono
 						.<DatabaseStageEntry<T>>fromCallable(() -> {
-							if (!Arrays.equals(keyPrefix, key)) {
+							if (!LLUtils.equals(keyPrefix, key)) {
 								throw new IndexOutOfBoundsException("Found more than one element!");
 							}
 							return null;

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

@@ -1,8 +1,9 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBuf;
 import it.cavallium.dbengine.database.serialization.Serializer;
 
-public class SubStageGetterSingleBytes extends SubStageGetterSingle<byte[]> {
+public class SubStageGetterSingleBytes extends SubStageGetterSingle<ByteBuf> {
 
 	public SubStageGetterSingleBytes() {
 		super(Serializer.noop());

src/main/java/it/cavallium/dbengine/database/disk/IterateBound.java

@@ -0,0 +1,6 @@
+package it.cavallium.dbengine.database.disk;
+
+public enum IterateBound {
+	LOWER,
+	UPPER
+}

src/main/java/it/cavallium/dbengine/database/disk/LLLocalDatabaseConnection.java

@@ -36,14 +36,18 @@ public class LLLocalDatabaseConnection implements LLDatabaseConnection {
 	}
 
 	@Override
-	public Mono<LLLocalKeyValueDatabase> getDatabase(String name, List<Column> columns, boolean lowMemory) {
+	public Mono<LLLocalKeyValueDatabase> getDatabase(String name,
+			List<Column> columns,
+			boolean lowMemory,
+			boolean inMemory) {
 		return Mono
 				.fromCallable(() -> new LLLocalKeyValueDatabase(name,
 						basePath.resolve("database_" + name),
 						columns,
 						new LinkedList<>(),
 						crashIfWalError,
-						lowMemory
+						lowMemory,
+						inMemory
 				))
 				.subscribeOn(Schedulers.boundedElastic());
 	}
@@ -55,7 +59,8 @@ public class LLLocalDatabaseConnection implements LLDatabaseConnection {
 			TextFieldsSimilarity textFieldsSimilarity,
 			Duration queryRefreshDebounceTime,
 			Duration commitDebounceTime,
-			boolean lowMemory) {
+			boolean lowMemory,
+			boolean inMemory) {
 		return Mono
 				.fromCallable(() -> {
 					if (instancesCount != 1) {
@@ -66,7 +71,8 @@ public class LLLocalDatabaseConnection implements LLDatabaseConnection {
 								textFieldsSimilarity,
 								queryRefreshDebounceTime,
 								commitDebounceTime,
-								lowMemory
+								lowMemory,
+								inMemory
 						);
 					} else {
 						return new LLLocalLuceneIndex(basePath.resolve("lucene"),
@@ -76,6 +82,7 @@ public class LLLocalDatabaseConnection implements LLDatabaseConnection {
 								queryRefreshDebounceTime,
 								commitDebounceTime,
 								lowMemory,
+								inMemory,
 								null
 						);
 					}

src/main/java/it/cavallium/dbengine/database/disk/LLLocalEntryReactiveRocksIterator.java

@@ -1,5 +1,7 @@
 package it.cavallium.dbengine.database.disk;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.database.LLRange;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -7,17 +9,18 @@ import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 
-public class LLLocalEntryReactiveRocksIterator extends LLLocalReactiveRocksIterator<Entry<byte[], byte[]>> {
+public class LLLocalEntryReactiveRocksIterator extends LLLocalReactiveRocksIterator<Entry<ByteBuf, ByteBuf>> {
 
 	public LLLocalEntryReactiveRocksIterator(RocksDB db,
+			ByteBufAllocator alloc,
 			ColumnFamilyHandle cfh,
 			LLRange range,
 			ReadOptions readOptions) {
-		super(db, cfh, range, readOptions, true);
+		super(db, alloc, cfh, range, readOptions, true);
 	}
 
 	@Override
-	public Entry<byte[], byte[]> getEntry(byte[] key, byte[] value) {
+	public Entry<ByteBuf, ByteBuf> getEntry(ByteBuf key, ByteBuf value) {
 		return Map.entry(key, value);
 	}
 }

src/main/java/it/cavallium/dbengine/database/disk/LLLocalGroupedEntryReactiveRocksIterator.java

@@ -1,5 +1,7 @@
 package it.cavallium.dbengine.database.disk;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.database.LLRange;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -8,19 +10,18 @@ import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 
 public class LLLocalGroupedEntryReactiveRocksIterator extends
-		LLLocalGroupedReactiveRocksIterator<Entry<byte[], byte[]>> {
+		LLLocalGroupedReactiveRocksIterator<Entry<ByteBuf, ByteBuf>> {
 
-	public LLLocalGroupedEntryReactiveRocksIterator(RocksDB db,
-			ColumnFamilyHandle cfh,
+	public LLLocalGroupedEntryReactiveRocksIterator(RocksDB db, ByteBufAllocator alloc, ColumnFamilyHandle cfh,
 			int prefixLength,
 			LLRange range,
 			ReadOptions readOptions,
 			String debugName) {
-		super(db, cfh, prefixLength, range, readOptions, false, true);
+		super(db, alloc, cfh, prefixLength, range, readOptions, false, true);
 	}
 
 	@Override
-	public Entry<byte[], byte[]> getEntry(byte[] key, byte[] value) {
+	public Entry<ByteBuf, ByteBuf> getEntry(ByteBuf key, ByteBuf value) {
 		return Map.entry(key, value);
 	}
 }

src/main/java/it/cavallium/dbengine/database/disk/LLLocalGroupedKeyReactiveRocksIterator.java

@@ -1,23 +1,26 @@
 package it.cavallium.dbengine.database.disk;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.database.LLRange;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 
-public class LLLocalGroupedKeyReactiveRocksIterator extends LLLocalGroupedReactiveRocksIterator<byte[]> {
+public class LLLocalGroupedKeyReactiveRocksIterator extends LLLocalGroupedReactiveRocksIterator<ByteBuf> {
 
 	public LLLocalGroupedKeyReactiveRocksIterator(RocksDB db,
+			ByteBufAllocator alloc,
 			ColumnFamilyHandle cfh,
 			int prefixLength,
 			LLRange range,
 			ReadOptions readOptions,
 			String debugName) {
-		super(db, cfh, prefixLength, range, readOptions, true, false);
+		super(db, alloc, cfh, prefixLength, range, readOptions, true, false);
 	}
 
 	@Override
-	public byte[] getEntry(byte[] key, byte[] value) {
+	public ByteBuf getEntry(ByteBuf key, ByteBuf value) {
 		return key;
 	}
 }

src/main/java/it/cavallium/dbengine/database/disk/LLLocalGroupedReactiveRocksIterator.java

@@ -2,21 +2,24 @@ package it.cavallium.dbengine.database.disk;
 
 import static it.cavallium.dbengine.database.disk.LLLocalDictionary.getRocksIterator;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.ByteBufUtil;
 import it.cavallium.dbengine.database.LLRange;
+import it.cavallium.dbengine.database.LLUtils;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
-import java.util.Arrays;
 import java.util.List;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksMutableObject;
 import reactor.core.publisher.Flux;
+import static io.netty.buffer.Unpooled.*;
 
 public abstract class LLLocalGroupedReactiveRocksIterator<T> {
 
-	private static final byte[] EMPTY = new byte[0];
-
 	private final RocksDB db;
+	private final ByteBufAllocator alloc;
 	private final ColumnFamilyHandle cfh;
 	private final int prefixLength;
 	private final LLRange range;
@@ -24,14 +27,14 @@ public abstract class LLLocalGroupedReactiveRocksIterator<T> {
 	private final boolean canFillCache;
 	private final boolean readValues;
 
-	public LLLocalGroupedReactiveRocksIterator(RocksDB db,
-			ColumnFamilyHandle cfh,
+	public LLLocalGroupedReactiveRocksIterator(RocksDB db, ByteBufAllocator alloc, ColumnFamilyHandle cfh,
 			int prefixLength,
 			LLRange range,
 			ReadOptions readOptions,
 			boolean canFillCache,
 			boolean readValues) {
 		this.db = db;
+		this.alloc = alloc;
 		this.cfh = cfh;
 		this.prefixLength = prefixLength;
 		this.range = range;
@@ -50,18 +53,33 @@ public abstract class LLLocalGroupedReactiveRocksIterator<T> {
 				}, (tuple, sink) -> {
 					var rocksIterator = tuple.getT1();
 					ObjectArrayList<T> values = new ObjectArrayList<>();
-					byte[] firstGroupKey = null;
+					ByteBuf firstGroupKey = null;
 
-					while (rocksIterator.isValid()) {
-						byte[] key = rocksIterator.key();
-						if (firstGroupKey == null) {
-							firstGroupKey = key;
-						} else if (!Arrays.equals(firstGroupKey, 0, prefixLength, key, 0, prefixLength)) {
-							break;
+					try {
+						while (rocksIterator.isValid()) {
+							ByteBuf key = LLUtils.readDirectNioBuffer(alloc, rocksIterator::key);
+							try {
+								if (firstGroupKey == null) {
+									firstGroupKey = key.retainedSlice();
+								} else if (!ByteBufUtil.equals(firstGroupKey, 0, key, 0, prefixLength)) {
+									break;
+								}
+								ByteBuf value = readValues ? LLUtils.readDirectNioBuffer(alloc, rocksIterator::value) : EMPTY_BUFFER;
+								try {
+									rocksIterator.next();
+									T entry = getEntry(key.retain(), value.retain());
+									values.add(entry);
+								} finally {
+									value.release();
+								}
+							} finally {
+								key.release();
+							}
+						}
+					} finally {
+						if (firstGroupKey != null) {
+							firstGroupKey.release();
 						}
-						byte[] value = readValues ? rocksIterator.value() : EMPTY;
-						rocksIterator.next();
-						values.add(getEntry(key, value));
 					}
 					if (!values.isEmpty()) {
 						sink.next(values);
@@ -72,10 +90,11 @@ public abstract class LLLocalGroupedReactiveRocksIterator<T> {
 				}, tuple -> {
 					var rocksIterator = tuple.getT1();
 					rocksIterator.close();
-					tuple.getT2().ifPresent(RocksMutableObject::close);
-					tuple.getT3().ifPresent(RocksMutableObject::close);
+					tuple.getT2().release();
+					tuple.getT3().release();
+					range.release();
 				});
 	}
 
-	public abstract T getEntry(byte[] key, byte[] value);
+	public abstract T getEntry(ByteBuf key, ByteBuf value);
 }

src/main/java/it/cavallium/dbengine/database/disk/LLLocalKeyPrefixReactiveRocksIterator.java

@@ -1,18 +1,22 @@
 package it.cavallium.dbengine.database.disk;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.ByteBufUtil;
 import it.cavallium.dbengine.database.LLRange;
+import it.cavallium.dbengine.database.LLUtils;
 import java.util.Arrays;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksMutableObject;
 import reactor.core.publisher.Flux;
+import static io.netty.buffer.Unpooled.*;
 
 public class LLLocalKeyPrefixReactiveRocksIterator {
 
-	private static final byte[] EMPTY = new byte[0];
-
 	private final RocksDB db;
+	private final ByteBufAllocator alloc;
 	private final ColumnFamilyHandle cfh;
 	private final int prefixLength;
 	private final LLRange range;
@@ -20,14 +24,14 @@ public class LLLocalKeyPrefixReactiveRocksIterator {
 	private final boolean canFillCache;
 	private final String debugName;
 
-	public LLLocalKeyPrefixReactiveRocksIterator(RocksDB db,
-			ColumnFamilyHandle cfh,
+	public LLLocalKeyPrefixReactiveRocksIterator(RocksDB db, ByteBufAllocator alloc, ColumnFamilyHandle cfh,
 			int prefixLength,
 			LLRange range,
 			ReadOptions readOptions,
 			boolean canFillCache,
 			String debugName) {
 		this.db = db;
+		this.alloc = alloc;
 		this.cfh = cfh;
 		this.prefixLength = prefixLength;
 		this.range = range;
@@ -37,7 +41,7 @@ public class LLLocalKeyPrefixReactiveRocksIterator {
 	}
 
 
-	public Flux<byte[]> flux() {
+	public Flux<ByteBuf> flux() {
 		return Flux
 				.generate(() -> {
 					var readOptions = new ReadOptions(this.readOptions);
@@ -45,32 +49,42 @@ public class LLLocalKeyPrefixReactiveRocksIterator {
 						//readOptions.setReadaheadSize(2 * 1024 * 1024);
 						readOptions.setFillCache(canFillCache);
 					}
-					return LLLocalDictionary.getRocksIterator(readOptions, range, db, cfh);
+					return LLLocalDictionary.getRocksIterator(readOptions, range.retain(), db, cfh);
 				}, (tuple, sink) -> {
 					var rocksIterator = tuple.getT1();
-					byte[] firstGroupKey = null;
-
-					while (rocksIterator.isValid()) {
-						byte[] key = rocksIterator.key();
-						if (firstGroupKey == null) {
-							firstGroupKey = key;
-						} else if (!Arrays.equals(firstGroupKey, 0, prefixLength, key, 0, prefixLength)) {
-							break;
+					ByteBuf firstGroupKey = null;
+					try {
+						while (rocksIterator.isValid()) {
+							ByteBuf key = LLUtils.readDirectNioBuffer(alloc, rocksIterator::key);
+							try {
+								if (firstGroupKey == null) {
+									firstGroupKey = key.retain();
+								} else if (!ByteBufUtil.equals(firstGroupKey, 0, key, 0, prefixLength)) {
+									break;
+								}
+								rocksIterator.next();
+							} finally {
+								key.release();
+							}
+						}
+						if (firstGroupKey != null) {
+							var groupKeyPrefix = firstGroupKey.slice(0, prefixLength);
+							sink.next(groupKeyPrefix.retain());
+						} else {
+							sink.complete();
+						}
+					} finally {
+						if (firstGroupKey != null) {
+							firstGroupKey.release();
 						}
-						rocksIterator.next();
-					}
-					if (firstGroupKey != null) {
-						var groupKeyPrefix = Arrays.copyOf(firstGroupKey, prefixLength);
-						sink.next(groupKeyPrefix);
-					} else {
-						sink.complete();
 					}
 					return tuple;
 				}, tuple -> {
 					var rocksIterator = tuple.getT1();
 					rocksIterator.close();
-					tuple.getT2().ifPresent(RocksMutableObject::close);
-					tuple.getT3().ifPresent(RocksMutableObject::close);
+					tuple.getT2().release();
+					tuple.getT3().release();
+					range.release();
 				});
 	}
 

src/main/java/it/cavallium/dbengine/database/disk/LLLocalKeyReactiveRocksIterator.java

@@ -1,21 +1,24 @@
 package it.cavallium.dbengine.database.disk;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.database.LLRange;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 
-public class LLLocalKeyReactiveRocksIterator extends LLLocalReactiveRocksIterator<byte[]> {
+public class LLLocalKeyReactiveRocksIterator extends LLLocalReactiveRocksIterator<ByteBuf> {
 
 	public LLLocalKeyReactiveRocksIterator(RocksDB db,
+			ByteBufAllocator alloc,
 			ColumnFamilyHandle cfh,
 			LLRange range,
 			ReadOptions readOptions) {
-		super(db, cfh, range, readOptions, false);
+		super(db, alloc, cfh, range, readOptions, false);
 	}
 
 	@Override
-	public byte[] getEntry(byte[] key, byte[] value) {
+	public ByteBuf getEntry(ByteBuf key, ByteBuf value) {
 		return key;
 	}
 }

src/main/java/it/cavallium/dbengine/database/disk/LLLocalKeyValueDatabase.java

@@ -59,6 +59,7 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 
 	private final Scheduler dbScheduler;
 	private final Path dbPath;
+	private final boolean inMemory;
 	private final String name;
 	private RocksDB db;
 	private final Map<Column, ColumnFamilyHandle> handles;
@@ -66,7 +67,7 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 	private final AtomicLong nextSnapshotNumbers = new AtomicLong(1);
 
 	public LLLocalKeyValueDatabase(String name, Path path, List<Column> columns, List<ColumnFamilyHandle> handles,
-			boolean crashIfWalError, boolean lowMemory) throws IOException {
+			boolean crashIfWalError, boolean lowMemory, boolean inMemory) throws IOException {
 		Options options = openRocksDb(path, crashIfWalError, lowMemory);
 		try {
 			List<ColumnFamilyDescriptor> descriptors = new LinkedList<>();
@@ -83,6 +84,7 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 			String dbPathString = databasesDirPath.toString() + File.separatorChar + path.getFileName();
 			Path dbPath = Paths.get(dbPathString);
 			this.dbPath = dbPath;
+			this.inMemory = inMemory;
 			this.name = name;
 			this.dbScheduler = Schedulers.newBoundedElastic(lowMemory ? Runtime.getRuntime().availableProcessors()
 							: Math.max(8, Runtime.getRuntime().availableProcessors()),
@@ -92,12 +94,17 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 					true
 			);
 
-			createIfNotExists(descriptors, options, dbPath, dbPathString);
+			createIfNotExists(descriptors, options, inMemory, this.dbPath, dbPathString);
 			// Create all column families that don't exist
-			createAllColumns(descriptors, options, dbPathString);
+			createAllColumns(descriptors, options, inMemory, dbPathString);
 
 			// a factory method that returns a RocksDB instance
-			this.db = RocksDB.open(new DBOptions(options), dbPathString, descriptors, handles);
+			this.db = RocksDB.open(new DBOptions(options),
+					dbPathString,
+					inMemory ? List.of(DEFAULT_COLUMN_FAMILY) : descriptors,
+					handles
+			);
+			createInMemoryColumns(descriptors, inMemory, handles);
 			this.handles = new HashMap<>();
 			for (int i = 0; i < columns.size(); i++) {
 				this.handles.put(columns.get(i), handles.get(i));
@@ -252,8 +259,10 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 		return options;
 	}
 
-	private void createAllColumns(List<ColumnFamilyDescriptor> totalDescriptors, Options options,
-			String dbPathString) throws RocksDBException {
+	private void createAllColumns(List<ColumnFamilyDescriptor> totalDescriptors, Options options, boolean inMemory, String dbPathString) throws RocksDBException {
+		if (inMemory) {
+			return;
+		}
 		List<byte[]> columnFamiliesToCreate = new LinkedList<>();
 
 		for (ColumnFamilyDescriptor descriptor : totalDescriptors) {
@@ -293,8 +302,35 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 		flushAndCloseDb(db, handles);
 	}
 
-	private void createIfNotExists(List<ColumnFamilyDescriptor> descriptors, Options options,
-			Path dbPath, String dbPathString) throws RocksDBException {
+	private void createInMemoryColumns(List<ColumnFamilyDescriptor> totalDescriptors,
+			boolean inMemory,
+			List<ColumnFamilyHandle> handles)
+			throws RocksDBException {
+		if (!inMemory) {
+			return;
+		}
+		List<byte[]> columnFamiliesToCreate = new LinkedList<>();
+
+		for (ColumnFamilyDescriptor descriptor : totalDescriptors) {
+			columnFamiliesToCreate.add(descriptor.getName());
+		}
+
+		for (byte[] name : columnFamiliesToCreate) {
+			if (!Arrays.equals(name, DEFAULT_COLUMN_FAMILY.getName())) {
+				var descriptor = new ColumnFamilyDescriptor(name);
+				handles.add(db.createColumnFamily(descriptor));
+			}
+		}
+	}
+
+	private void createIfNotExists(List<ColumnFamilyDescriptor> descriptors,
+			Options options,
+			boolean inMemory,
+			Path dbPath,
+			String dbPathString) throws RocksDBException {
+		if (inMemory) {
+			return;
+		}
 		if (Files.notExists(dbPath)) {
 			// Check if handles are all different
 			var descriptorsSet = new HashSet<>(descriptors);
@@ -318,7 +354,9 @@ public class LLLocalKeyValueDatabase implements LLKeyValueDatabase {
 				handles.add(db.createColumnFamily(columnFamilyDescriptor));
 			}
 
-			flushAndCloseDb(db, handles);
+			if (!inMemory) {
+				flushAndCloseDb(db, handles);
+			}
 		}
 	}
 

src/main/java/it/cavallium/dbengine/database/disk/LLLocalLuceneIndex.java

@@ -53,6 +53,9 @@ import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.search.similarities.TFIDFSimilarity;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
+import org.apache.lucene.store.MMapDirectory;
+import org.apache.lucene.store.RAMDirectory;
+import org.apache.solr.core.RAMDirectoryFactory;
 import org.jetbrains.annotations.Nullable;
 import org.warp.commonutils.log.Logger;
 import org.warp.commonutils.log.LoggerFactory;
@@ -113,13 +116,12 @@ public class LLLocalLuceneIndex implements LLLuceneIndex {
 			TextFieldsSimilarity similarity,
 			Duration queryRefreshDebounceTime,
 			Duration commitDebounceTime,
-			boolean lowMemory,
-			@Nullable LLSearchCollectionStatisticsGetter distributedCollectionStatisticsGetter) throws IOException {
+			boolean lowMemory, boolean inMemory, @Nullable LLSearchCollectionStatisticsGetter distributedCollectionStatisticsGetter) throws IOException {
 		if (name.length() == 0) {
 			throw new IOException("Empty lucene database name");
 		}
 		Path directoryPath = luceneBasePath.resolve(name + ".lucene.db");
-		this.directory = FSDirectory.open(directoryPath);
+		this.directory = inMemory ? new RAMDirectory() : FSDirectory.open(directoryPath);
 		this.luceneIndexName = name;
 		this.snapshotter = new SnapshotDeletionPolicy(new KeepOnlyLastCommitDeletionPolicy());
 		this.lowMemory = lowMemory;

src/main/java/it/cavallium/dbengine/database/disk/LLLocalMultiLuceneIndex.java

@@ -58,7 +58,7 @@ public class LLLocalMultiLuceneIndex implements LLLuceneIndex {
 			TextFieldsSimilarity textFieldsSimilarity,
 			Duration queryRefreshDebounceTime,
 			Duration commitDebounceTime,
-			boolean lowMemory) throws IOException {
+			boolean lowMemory, boolean inMemory) throws IOException {
 
 		if (instancesCount <= 1 || instancesCount > 100) {
 			throw new IOException("Unsupported instances count: " + instancesCount);
@@ -79,8 +79,7 @@ public class LLLocalMultiLuceneIndex implements LLLuceneIndex {
 					textFieldsSimilarity,
 					queryRefreshDebounceTime,
 					commitDebounceTime,
-					lowMemory,
-					(indexSearcher, field, distributedPre, actionId) -> distributedCustomCollectionStatistics(finalI,
+					lowMemory, inMemory, (indexSearcher, field, distributedPre, actionId) -> distributedCustomCollectionStatistics(finalI,
 							indexSearcher,
 							field,
 							distributedPre,

src/main/java/it/cavallium/dbengine/database/disk/LLLocalReactiveRocksIterator.java

@@ -2,29 +2,34 @@ package it.cavallium.dbengine.database.disk;
 
 import static it.cavallium.dbengine.database.disk.LLLocalDictionary.getRocksIterator;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
 import it.cavallium.dbengine.database.LLRange;
+import it.cavallium.dbengine.database.LLUtils;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.ReadOptions;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksMutableObject;
 import reactor.core.publisher.Flux;
+import static io.netty.buffer.Unpooled.*;
 
 public abstract class LLLocalReactiveRocksIterator<T> {
 
-	private static final byte[] EMPTY = new byte[0];
-
 	private final RocksDB db;
+	private final ByteBufAllocator alloc;
 	private final ColumnFamilyHandle cfh;
 	private final LLRange range;
 	private final ReadOptions readOptions;
 	private final boolean readValues;
 
 	public LLLocalReactiveRocksIterator(RocksDB db,
+			ByteBufAllocator alloc,
 			ColumnFamilyHandle cfh,
 			LLRange range,
 			ReadOptions readOptions,
 			boolean readValues) {
 		this.db = db;
+		this.alloc = alloc;
 		this.cfh = cfh;
 		this.range = range;
 		this.readOptions = readOptions;
@@ -39,14 +44,22 @@ public abstract class LLLocalReactiveRocksIterator<T> {
 						readOptions.setReadaheadSize(2 * 1024 * 1024);
 						readOptions.setFillCache(false);
 					}
-					return getRocksIterator(readOptions, range, db, cfh);
+					return getRocksIterator(readOptions, range.retain(), db, cfh);
 				}, (tuple, sink) -> {
 					var rocksIterator = tuple.getT1();
 					if (rocksIterator.isValid()) {
-						byte[] key = rocksIterator.key();
-						byte[] value = readValues ? rocksIterator.value() : EMPTY;
-						rocksIterator.next();
-						sink.next(getEntry(key, value));
+						ByteBuf key = LLUtils.readDirectNioBuffer(alloc, rocksIterator::key);
+						try {
+							ByteBuf value = readValues ? LLUtils.readDirectNioBuffer(alloc, rocksIterator::value) : EMPTY_BUFFER;
+							try {
+								rocksIterator.next();
+								sink.next(getEntry(key.retain(), value.retain()));
+							} finally {
+								value.release();
+							}
+						} finally {
+							key.release();
+						}
 					} else {
 						sink.complete();
 					}
@@ -54,10 +67,10 @@ public abstract class LLLocalReactiveRocksIterator<T> {
 				}, tuple -> {
 					var rocksIterator = tuple.getT1();
 					rocksIterator.close();
-					tuple.getT2().ifPresent(RocksMutableObject::close);
-					tuple.getT3().ifPresent(RocksMutableObject::close);
+					tuple.getT2().release();
+					tuple.getT3().release();
 				});
 	}
 
-	public abstract T getEntry(byte[] key, byte[] value);
+	public abstract T getEntry(ByteBuf key, ByteBuf value);
 }

src/main/java/it/cavallium/dbengine/database/serialization/CodecSerializer.java

@@ -3,13 +3,14 @@ package it.cavallium.dbengine.database.serialization;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufInputStream;
 import io.netty.buffer.ByteBufOutputStream;
+import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.buffer.Unpooled;
 import java.io.IOError;
 import java.io.IOException;
 import org.jetbrains.annotations.NotNull;
 import org.warp.commonutils.error.IndexOutOfBoundsException;
 
-public class CodecSerializer<A> implements Serializer<A, byte[]> {
+public class CodecSerializer<A> implements Serializer<A, ByteBuf> {
 
 	private final Codecs<A> deserializationCodecs;
 	private final Codec<A> serializationCodec;
@@ -34,9 +35,8 @@ public class CodecSerializer<A> implements Serializer<A, byte[]> {
 	}
 
 	@Override
-	public @NotNull A deserialize(byte @NotNull [] serialized) {
-		ByteBuf buf = Unpooled.wrappedBuffer(serialized);
-		try (var is = new ByteBufInputStream(buf)) {
+	public @NotNull A deserialize(@NotNull ByteBuf serialized) {
+		try (var is = new ByteBufInputStream(serialized)) {
 			int codecId;
 			if (microCodecs) {
 				codecId = is.readUnsignedByte();
@@ -48,12 +48,14 @@ public class CodecSerializer<A> implements Serializer<A, byte[]> {
 		} catch (IOException ex) {
 			// This shouldn't happen
 			throw new IOError(ex);
+		} finally {
+			serialized.release();
 		}
 	}
 
 	@Override
-	public byte @NotNull [] serialize(@NotNull A deserialized) {
-		ByteBuf buf = Unpooled.buffer(256);
+	public @NotNull ByteBuf serialize(@NotNull A deserialized) {
+		ByteBuf buf = PooledByteBufAllocator.DEFAULT.directBuffer();
 		try (var os = new ByteBufOutputStream(buf)) {
 			if (microCodecs) {
 				os.writeByte(serializationCodecId);
@@ -61,14 +63,11 @@ public class CodecSerializer<A> implements Serializer<A, byte[]> {
 				os.writeInt(serializationCodecId);
 			}
 			serializationCodec.serialize(os, deserialized);
-			os.flush();
-			var bytes = new byte[buf.readableBytes()];
-			buf.readBytes(bytes);
-			return bytes;
 		} catch (IOException ex) {
 			// This shouldn't happen
 			throw new IOError(ex);
 		}
+		return buf;
 	}
 
 	@SuppressWarnings("unused")

src/main/java/it/cavallium/dbengine/database/serialization/Serializer.java

@@ -1,5 +1,9 @@
 package it.cavallium.dbengine.database.serialization;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.buffer.PooledByteBufAllocator;
+import java.nio.charset.StandardCharsets;
 import org.jetbrains.annotations.NotNull;
 
 public interface Serializer<A, B> {
@@ -8,19 +12,50 @@ public interface Serializer<A, B> {
 
 	@NotNull B serialize(@NotNull A deserialized);
 
-	Serializer<byte[], byte[]> NOOP_SERIALIZER = new Serializer<>() {
+	Serializer<ByteBuf, ByteBuf> NOOP_SERIALIZER = new Serializer<>() {
 		@Override
-		public byte @NotNull [] deserialize(byte @NotNull [] serialized) {
-			return serialized;
+		public @NotNull ByteBuf deserialize(@NotNull ByteBuf serialized) {
+			try {
+				return serialized.retainedSlice();
+			} finally {
+				serialized.release();
+			}
 		}
 
 		@Override
-		public byte @NotNull [] serialize(byte @NotNull [] deserialized) {
-			return deserialized;
+		public @NotNull ByteBuf serialize(@NotNull ByteBuf deserialized) {
+			try {
+				return deserialized.retainedSlice();
+			} finally {
+				deserialized.release();
+			}
 		}
 	};
 
-	static Serializer<byte[], byte[]> noop() {
+	Serializer<String, ByteBuf> UTF8_SERIALIZER = new Serializer<>() {
+		@Override
+		public @NotNull String deserialize(@NotNull ByteBuf serialized) {
+			try {
+				return serialized.toString(StandardCharsets.UTF_8);
+			} finally {
+				serialized.release();
+			}
+		}
+
+		@Override
+		public @NotNull ByteBuf serialize(@NotNull String deserialized) {
+			// UTF-8 uses max. 3 bytes per char, so calculate the worst case.
+			ByteBuf buf = PooledByteBufAllocator.DEFAULT.directBuffer(ByteBufUtil.utf8MaxBytes(deserialized));
+			ByteBufUtil.writeUtf8(buf, deserialized);
+			return buf;
+		}
+	};
+
+	static Serializer<ByteBuf, ByteBuf> noop() {
 		return NOOP_SERIALIZER;
 	}
+
+	static Serializer<String, ByteBuf> utf8() {
+		return UTF8_SERIALIZER;
+	}
 }

src/main/java/it/cavallium/dbengine/database/serialization/SerializerFixedBinaryLength.java

@@ -2,6 +2,12 @@ package it.cavallium.dbengine.database.serialization;
 
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.buffer.PooledByteBufAllocator;
+import java.io.NotSerializableException;
+import java.nio.charset.StandardCharsets;
+import org.apache.commons.lang3.SerializationException;
 import org.jetbrains.annotations.NotNull;
 
 @SuppressWarnings("unused")
@@ -9,18 +15,31 @@ public interface SerializerFixedBinaryLength<A, B> extends Serializer<A, B> {
 
 	int getSerializedBinaryLength();
 
-	static SerializerFixedBinaryLength<byte[], byte[]> noop(int length) {
+	static SerializerFixedBinaryLength<ByteBuf, ByteBuf> noop(int length) {
 		return new SerializerFixedBinaryLength<>() {
 			@Override
-			public byte @NotNull [] deserialize(byte @NotNull [] serialized) {
-				assert serialized.length == getSerializedBinaryLength();
-				return serialized;
+			public @NotNull ByteBuf deserialize(@NotNull ByteBuf serialized) {
+				try {
+					if (serialized.readableBytes() != getSerializedBinaryLength()) {
+						throw new IllegalArgumentException(
+								"Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to deserialize an element with "
+										+ serialized.readableBytes() + " bytes instead");
+					}
+					return serialized.retain();
+				} finally {
+					serialized.release();
+				}
 			}
 
 			@Override
-			public byte @NotNull [] serialize(byte @NotNull [] deserialized) {
-				assert deserialized.length == getSerializedBinaryLength();
-				return deserialized;
+			public @NotNull ByteBuf serialize(@NotNull ByteBuf deserialized) {
+				ByteBuf buf = deserialized.retain();
+				if (buf.readableBytes() != getSerializedBinaryLength()) {
+					throw new IllegalArgumentException(
+							"Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to serialize an element with "
+									+ buf.readableBytes() + " bytes instead");
+				}
+				return buf;
 			}
 
 			@Override
@@ -30,17 +49,65 @@ public interface SerializerFixedBinaryLength<A, B> extends Serializer<A, B> {
 		};
 	}
 
-	static SerializerFixedBinaryLength<Integer, byte[]> intSerializer() {
+	static SerializerFixedBinaryLength<String, ByteBuf> utf8(int length) {
 		return new SerializerFixedBinaryLength<>() {
 			@Override
-			public @NotNull Integer deserialize(byte @NotNull [] serialized) {
-				assert serialized.length == getSerializedBinaryLength();
-				return Ints.fromByteArray(serialized);
+			public @NotNull String deserialize(@NotNull ByteBuf serialized) {
+				try {
+					if (serialized.readableBytes() != getSerializedBinaryLength()) {
+						throw new SerializationException(
+								"Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to deserialize an element with "
+										+ serialized.readableBytes() + " bytes instead");
+					}
+					return serialized.toString(StandardCharsets.UTF_8);
+				} finally {
+					serialized.release();
+				}
 			}
 
 			@Override
-			public byte @NotNull [] serialize(@NotNull Integer deserialized) {
-				return Ints.toByteArray(deserialized);
+			public @NotNull ByteBuf serialize(@NotNull String deserialized) {
+				// UTF-8 uses max. 3 bytes per char, so calculate the worst case.
+				ByteBuf buf = PooledByteBufAllocator.DEFAULT.directBuffer(ByteBufUtil.utf8MaxBytes(deserialized));
+				try {
+					ByteBufUtil.writeUtf8(buf, deserialized);
+					if (buf.readableBytes() != getSerializedBinaryLength()) {
+						throw new SerializationException("Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to serialize an element with "
+								+ buf.readableBytes() + " bytes instead");
+					}
+					return buf.retain();
+				} finally {
+					buf.release();
+				}
+			}
+
+			@Override
+			public int getSerializedBinaryLength() {
+				return length;
+			}
+		};
+	}
+
+	static SerializerFixedBinaryLength<Integer, ByteBuf> intSerializer() {
+		return new SerializerFixedBinaryLength<>() {
+			@Override
+			public @NotNull Integer deserialize(@NotNull ByteBuf serialized) {
+				try {
+					if (serialized.readableBytes() != getSerializedBinaryLength()) {
+						throw new IllegalArgumentException(
+								"Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to deserialize an element with "
+										+ serialized.readableBytes() + " bytes instead");
+					}
+					return serialized.readInt();
+				} finally {
+					serialized.release();
+				}
+			}
+
+			@Override
+			public @NotNull ByteBuf serialize(@NotNull Integer deserialized) {
+				ByteBuf buf = PooledByteBufAllocator.DEFAULT.directBuffer(Integer.BYTES, Integer.BYTES);
+				return buf.writeInt(deserialized);
 			}
 
 			@Override
@@ -50,17 +117,26 @@ public interface SerializerFixedBinaryLength<A, B> extends Serializer<A, B> {
 		};
 	}
 
-	static SerializerFixedBinaryLength<Long, byte[]> longSerializer() {
+	static SerializerFixedBinaryLength<Long, ByteBuf> longSerializer() {
 		return new SerializerFixedBinaryLength<>() {
 			@Override
-			public @NotNull Long deserialize(byte @NotNull [] serialized) {
-				assert serialized.length == getSerializedBinaryLength();
-				return Longs.fromByteArray(serialized);
+			public @NotNull Long deserialize(@NotNull ByteBuf serialized) {
+				try {
+					if (serialized.readableBytes() != getSerializedBinaryLength()) {
+						throw new IllegalArgumentException(
+								"Fixed serializer with " + getSerializedBinaryLength() + " bytes has tried to deserialize an element with "
+										+ serialized.readableBytes() + " bytes instead");
+					}
+					return serialized.readLong();
+				} finally {
+					serialized.release();
+				}
 			}
 
 			@Override
-			public byte @NotNull [] serialize(@NotNull Long deserialized) {
-				return Longs.toByteArray(deserialized);
+			public @NotNull ByteBuf serialize(@NotNull Long deserialized) {
+				ByteBuf buf = PooledByteBufAllocator.DEFAULT.directBuffer(Integer.BYTES, Integer.BYTES);
+				return buf.writeLong(deserialized);
 			}
 
 			@Override

src/main/java/org/rocksdb/CappedWriteBatch.java

@@ -1,6 +1,11 @@
-package it.cavallium.dbengine.database.disk;
+package org.rocksdb;
 
+import io.netty.buffer.ByteBuf;
+import it.cavallium.dbengine.database.LLUtils;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+import org.rocksdb.AbstractWriteBatch;
 import org.rocksdb.ColumnFamilyHandle;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksDBException;
@@ -10,13 +15,13 @@ import org.rocksdb.WriteOptions;
 import org.warp.commonutils.concurrency.atomicity.NotAtomic;
 
 @NotAtomic
-public class CappedWriteBatch implements WriteBatchInterface, AutoCloseable {
+public class CappedWriteBatch extends WriteBatch {
 
 	private final RocksDB db;
 	private final int cap;
 	private final WriteOptions writeOptions;
-
-	private final WriteBatch writeBatch;
+	
+	private final List<ByteBuf> buffersToRelease;
 
 	/**
 	 * @param cap The limit of operations
@@ -26,158 +31,224 @@ public class CappedWriteBatch implements WriteBatchInterface, AutoCloseable {
 			int reservedWriteBatchSize,
 			long maxWriteBatchSize,
 			WriteOptions writeOptions) {
+		super(reservedWriteBatchSize);
 		this.db = db;
 		this.cap = cap;
 		this.writeOptions = writeOptions;
-		this.writeBatch = new WriteBatch(reservedWriteBatchSize);
-		this.writeBatch.setMaxBytes(maxWriteBatchSize);
+		this.setMaxBytes(maxWriteBatchSize);
+		this.buffersToRelease = new ArrayList<>();
 	}
 
 	private synchronized void flushIfNeeded(boolean force) throws RocksDBException {
-		if (this.writeBatch.count() >= (force ? 1 : cap)) {
-			db.write(writeOptions, this.writeBatch);
-			this.writeBatch.clear();
+		if (this.count() >= (force ? 1 : cap)) {
+			db.write(writeOptions, this);
+			this.clear();
+			releaseAllBuffers();
 		}
 	}
 
+	private synchronized void releaseAllBuffers() {
+		for (ByteBuf byteBuffer : buffersToRelease) {
+			byteBuffer.release();
+		}
+		buffersToRelease.clear();
+	}
+
 	@Override
 	public synchronized int count() {
-		return writeBatch.count();
+		return super.count();
 	}
 
 	@Override
 	public synchronized void put(byte[] key, byte[] value) throws RocksDBException {
-		writeBatch.put(key, value);
+		super.put(key, value);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void put(ColumnFamilyHandle columnFamilyHandle, byte[] key, byte[] value) throws RocksDBException {
-		writeBatch.put(columnFamilyHandle, key, value);
+		super.put(columnFamilyHandle, key, value);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void put(ByteBuffer key, ByteBuffer value) throws RocksDBException {
-		writeBatch.put(key, value);
+		super.put(key, value);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void put(ColumnFamilyHandle columnFamilyHandle, ByteBuffer key, ByteBuffer value) throws RocksDBException {
-		writeBatch.put(columnFamilyHandle, key, value);
+		super.put(columnFamilyHandle, key, value);
+		flushIfNeeded(false);
+	}
+
+	public synchronized void put(ColumnFamilyHandle columnFamilyHandle, ByteBuf key, ByteBuf value) throws RocksDBException {
+		buffersToRelease.add(key);
+		buffersToRelease.add(value);
+		ByteBuf keyDirectBuf = key.retain();
+		ByteBuffer keyNioBuffer = LLUtils.toDirectFast(keyDirectBuf.retain());
+		if (keyNioBuffer == null) {
+			keyDirectBuf.release();
+			keyDirectBuf = LLUtils.toDirectCopy(key.retain());
+			keyNioBuffer = keyDirectBuf.nioBuffer();
+		}
+		try {
+			assert keyNioBuffer.isDirect();
+
+			ByteBuf valueDirectBuf = value.retain();
+			ByteBuffer valueNioBuffer = LLUtils.toDirectFast(valueDirectBuf.retain());
+			if (valueNioBuffer == null) {
+				valueDirectBuf.release();
+				valueDirectBuf = LLUtils.toDirectCopy(value.retain());
+				valueNioBuffer = valueDirectBuf.nioBuffer();
+			}
+			try {
+				assert valueNioBuffer.isDirect();
+				super.put(columnFamilyHandle, keyNioBuffer, valueNioBuffer);
+			} finally {
+				buffersToRelease.add(valueDirectBuf);
+			}
+		} finally {
+			buffersToRelease.add(keyDirectBuf);
+		}
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void merge(byte[] key, byte[] value) throws RocksDBException {
-		writeBatch.merge(key, value);
+		super.merge(key, value);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void merge(ColumnFamilyHandle columnFamilyHandle, byte[] key, byte[] value) throws RocksDBException {
-		writeBatch.merge(columnFamilyHandle, key, value);
+		super.merge(columnFamilyHandle, key, value);
 		flushIfNeeded(false);
 	}
 
 	@Deprecated
 	@Override
 	public synchronized void remove(byte[] key) throws RocksDBException {
-		writeBatch.remove(key);
+		super.remove(key);
 		flushIfNeeded(false);
 	}
 
 	@Deprecated
 	@Override
 	public synchronized void remove(ColumnFamilyHandle columnFamilyHandle, byte[] key) throws RocksDBException {
-		writeBatch.remove(columnFamilyHandle, key);
+		super.remove(columnFamilyHandle, key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void delete(byte[] key) throws RocksDBException {
-		writeBatch.delete(key);
+		super.delete(key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void delete(ColumnFamilyHandle columnFamilyHandle, byte[] key) throws RocksDBException {
-		writeBatch.delete(columnFamilyHandle, key);
+		super.delete(columnFamilyHandle, key);
+		flushIfNeeded(false);
+	}
+
+	public synchronized void delete(ColumnFamilyHandle columnFamilyHandle, ByteBuf key) throws RocksDBException {
+		buffersToRelease.add(key);
+		ByteBuf keyDirectBuf = key.retain();
+		ByteBuffer keyNioBuffer = LLUtils.toDirectFast(keyDirectBuf.retain());
+		if (keyNioBuffer == null) {
+			keyDirectBuf.release();
+			keyDirectBuf = LLUtils.toDirectCopy(key.retain());
+			keyNioBuffer = keyDirectBuf.nioBuffer();
+		}
+		try {
+			assert keyNioBuffer.isDirect();
+			removeDirect(nativeHandle_,
+					keyNioBuffer,
+					keyNioBuffer.position(),
+					keyNioBuffer.remaining(),
+					columnFamilyHandle.nativeHandle_
+			);
+			keyNioBuffer.position(keyNioBuffer.limit());
+		} finally {
+			buffersToRelease.add(keyDirectBuf);
+		}
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void singleDelete(byte[] key) throws RocksDBException {
-		writeBatch.singleDelete(key);
+		super.singleDelete(key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void singleDelete(ColumnFamilyHandle columnFamilyHandle, byte[] key) throws RocksDBException {
-		writeBatch.singleDelete(columnFamilyHandle, key);
+		super.singleDelete(columnFamilyHandle, key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void remove(ByteBuffer key) throws RocksDBException {
-		writeBatch.remove(key);
+		super.remove(key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void remove(ColumnFamilyHandle columnFamilyHandle, ByteBuffer key) throws RocksDBException {
-		writeBatch.remove(columnFamilyHandle, key);
+		super.remove(columnFamilyHandle, key);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void deleteRange(byte[] beginKey, byte[] endKey) throws RocksDBException {
-		writeBatch.deleteRange(beginKey, endKey);
+		super.deleteRange(beginKey, endKey);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void deleteRange(ColumnFamilyHandle columnFamilyHandle, byte[] beginKey, byte[] endKey)
 			throws RocksDBException {
-		writeBatch.deleteRange(columnFamilyHandle, beginKey, endKey);
+		super.deleteRange(columnFamilyHandle, beginKey, endKey);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void putLogData(byte[] blob) throws RocksDBException {
-		writeBatch.putLogData(blob);
+		super.putLogData(blob);
 		flushIfNeeded(false);
 	}
 
 	@Override
 	public synchronized void clear() {
-		writeBatch.clear();
+		super.clear();
+		releaseAllBuffers();
 	}
 
 	@Override
 	public synchronized void setSavePoint() {
-		writeBatch.setSavePoint();
+		super.setSavePoint();
 	}
 
 	@Override
 	public synchronized void rollbackToSavePoint() throws RocksDBException {
-		writeBatch.rollbackToSavePoint();
+		super.rollbackToSavePoint();
 	}
 
 	@Override
 	public synchronized void popSavePoint() throws RocksDBException {
-		writeBatch.popSavePoint();
+		super.popSavePoint();
 	}
 
 	@Override
 	public synchronized void setMaxBytes(long maxBytes) {
-		writeBatch.setMaxBytes(maxBytes);
+		super.setMaxBytes(maxBytes);
 	}
 
 	@Override
 	public synchronized WriteBatch getWriteBatch() {
-		return writeBatch;
+		return this;
 	}
 
 	public synchronized void writeToDbAndClose() throws RocksDBException {
@@ -186,6 +257,7 @@ public class CappedWriteBatch implements WriteBatchInterface, AutoCloseable {
 
 	@Override
 	public synchronized void close() {
-		writeBatch.close();
+		super.close();
+		releaseAllBuffers();
 	}
 }

src/test/java/it/cavallium/dbengine/client/DbTestUtils.java

@@ -0,0 +1,106 @@
+package it.cavallium.dbengine.client;
+
+import it.cavallium.dbengine.database.Column;
+import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.LLKeyValueDatabase;
+import it.cavallium.dbengine.database.UpdateMode;
+import it.cavallium.dbengine.database.collections.DatabaseMapDictionary;
+import it.cavallium.dbengine.database.collections.DatabaseMapDictionaryDeep;
+import it.cavallium.dbengine.database.collections.DatabaseMapDictionaryHashed;
+import it.cavallium.dbengine.database.collections.SubStageGetterHashMap;
+import it.cavallium.dbengine.database.collections.SubStageGetterMap;
+import it.cavallium.dbengine.database.disk.LLLocalDatabaseConnection;
+import it.cavallium.dbengine.database.serialization.Serializer;
+import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
+
+public class DbTestUtils {
+
+	public static final AtomicInteger dbId = new AtomicInteger(0);
+
+	public static <U> Flux<U> tempDb(Function<LLKeyValueDatabase, Publisher<U>> action) {
+		var wrkspcPath = Path.of("/tmp/.cache/tempdb-" + dbId.incrementAndGet() + "/");
+		return Flux.usingWhen(Mono
+						.<LLKeyValueDatabase>fromCallable(() -> {
+							if (Files.exists(wrkspcPath)) {
+								Files.walk(wrkspcPath).sorted(Comparator.reverseOrder()).forEach(file -> {
+									try {
+										Files.delete(file);
+									} catch (IOException ex) {
+										throw new CompletionException(ex);
+									}
+								});
+							}
+							Files.createDirectories(wrkspcPath);
+							return null;
+						})
+						.subscribeOn(Schedulers.boundedElastic())
+						.then(new LLLocalDatabaseConnection(wrkspcPath, true).connect())
+						.flatMap(conn -> conn.getDatabase("testdb",
+								List.of(Column.dictionary("testmap"), Column.special("ints"), Column.special("longs")),
+								false, true
+						)),
+				action,
+				db -> db.close().then(Mono.fromCallable(() -> {
+					if (Files.exists(wrkspcPath)) {
+						Files.walk(wrkspcPath).sorted(Comparator.reverseOrder()).forEach(file -> {
+							try {
+								Files.delete(file);
+							} catch (IOException ex) {
+								throw new CompletionException(ex);
+							}
+						});
+					}
+					return null;
+				}).subscribeOn(Schedulers.boundedElastic()))
+		);
+	}
+	public static Mono<? extends LLDictionary> tempDictionary(LLKeyValueDatabase database, UpdateMode updateMode) {
+		return tempDictionary(database, "testmap", updateMode);
+	}
+
+	public static Mono<? extends LLDictionary> tempDictionary(LLKeyValueDatabase database,
+			String name,
+			UpdateMode updateMode) {
+		return database.getDictionary(name, updateMode);
+	}
+
+	public static DatabaseMapDictionary<String, String> tempDatabaseMapDictionaryMap(
+			LLDictionary dictionary,
+			int keyBytes) {
+		return DatabaseMapDictionary.simple(dictionary, SerializerFixedBinaryLength.utf8(keyBytes), Serializer.utf8());
+	}
+
+	public static <T, U> DatabaseMapDictionaryDeep<String, Map<String, String>, DatabaseMapDictionary<String, String>> tempDatabaseMapDictionaryDeepMap(
+			LLDictionary dictionary,
+			int key1Bytes,
+			int key2Bytes) {
+		return DatabaseMapDictionaryDeep.deepTail(dictionary,
+				SerializerFixedBinaryLength.utf8(key1Bytes),
+				key2Bytes,
+				new SubStageGetterMap<>(SerializerFixedBinaryLength.utf8(key2Bytes), Serializer.UTF8_SERIALIZER)
+		);
+	}
+
+	public static <T, U> DatabaseMapDictionaryHashed<String, String, Integer> tempDatabaseMapDictionaryHashMap(
+			LLDictionary dictionary) {
+		return DatabaseMapDictionaryHashed.simple(dictionary,
+				Serializer.utf8(),
+				Serializer.utf8(),
+				String::hashCode,
+				SerializerFixedBinaryLength.intSerializer()
+		);
+	}
+}

src/test/java/it/cavallium/dbengine/client/OldDatabaseTests.java

@@ -2,15 +2,19 @@ package it.cavallium.dbengine.client;
 
 import static it.cavallium.dbengine.client.CompositeDatabasePartLocation.CompositeDatabasePartType.KV_DATABASE;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import it.cavallium.dbengine.database.Column;
 import it.cavallium.dbengine.database.LLKeyValueDatabase;
 import it.cavallium.dbengine.database.UpdateMode;
+import it.cavallium.dbengine.database.collections.DatabaseMapDictionary;
 import it.cavallium.dbengine.database.collections.DatabaseMapDictionaryDeep;
 import it.cavallium.dbengine.database.collections.SubStageGetterMap;
 import it.cavallium.dbengine.database.disk.LLLocalDatabaseConnection;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -20,6 +24,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import org.jetbrains.annotations.NotNull;
 import org.junit.jupiter.api.Test;
@@ -29,7 +34,61 @@ import reactor.core.scheduler.Schedulers;
 import reactor.test.StepVerifier;
 import reactor.util.function.Tuples;
 
-public class Database {
+public class OldDatabaseTests {
+
+	@Test
+	public void testDatabaseAddKeysAndCheckSize() {
+		LinkedHashSet<String> originalKeys = new LinkedHashSet<>(List.of("K1a", "K1b", "K1c"));
+
+		StepVerifier
+				.create(
+						tempDb()
+								.flatMap(db -> db
+										.getDictionary("testmap", UpdateMode.DISALLOW)
+										.map(dictionary -> DatabaseMapDictionary.simple(dictionary,
+												new FixedStringSerializer(3),
+												Serializer.noop()
+										))
+										.flatMap(collection -> Flux
+												.fromIterable(originalKeys)
+												.flatMap(k1 -> collection.putValue(k1, DUMMY_VALUE))
+												.then(collection.leavesCount(null, false))
+										)
+								)
+				)
+				.expectNext((long) originalKeys.size())
+				.verifyComplete();
+	}
+
+	@Test
+	public void testDeepDatabaseAddKeysAndCheckSize() {
+		LinkedHashSet<String> originalSuperKeys = new LinkedHashSet<>(List.of("K1a", "K1b", "K1c"));
+		LinkedHashSet<String> originalSubKeys = new LinkedHashSet<>(List.of("K2aa", "K2bb", "K2cc"));
+
+		StepVerifier
+				.create(
+						tempDb()
+								.flatMap(db -> db
+										.getDictionary("testmap", UpdateMode.DISALLOW)
+										.map(dictionary -> DatabaseMapDictionaryDeep.deepTail(dictionary,
+												new FixedStringSerializer(3),
+												4,
+												new SubStageGetterMap<>(new FixedStringSerializer(4), Serializer.noop())
+										))
+										.flatMap(collection -> Flux
+												.fromIterable(originalSuperKeys)
+												.flatMap(k1 -> collection.at(null, k1))
+												.flatMap(k1at -> Flux
+														.fromIterable(originalSubKeys)
+														.flatMap(k2 -> k1at.putValue(k2, DUMMY_VALUE))
+												)
+												.then(collection.leavesCount(null, false))
+										)
+								)
+				)
+				.expectNext((long) originalSuperKeys.size() * originalSubKeys.size())
+				.verifyComplete();
+	}
 
 	@Test
 	public void testDeepDatabaseAddKeysAndConvertToLongerOnes() {
@@ -53,7 +112,7 @@ public class Database {
 	}
 
 	public static <U> Mono<? extends LLKeyValueDatabase> tempDb() {
-		var wrkspcPath = Path.of("/tmp/.cache/tempdb/");
+		var wrkspcPath = Path.of("/tmp/.cache/tempdb-" + DbTestUtils.dbId.incrementAndGet() + "/");
 		return Mono
 				.fromCallable(() -> {
 					if (Files.exists(wrkspcPath)) {
@@ -72,10 +131,16 @@ public class Database {
 				})
 				.subscribeOn(Schedulers.boundedElastic())
 				.then(new LLLocalDatabaseConnection(wrkspcPath, true).connect())
-				.flatMap(conn -> conn.getDatabase("testdb", List.of(Column.dictionary("testmap")), false));
+				.flatMap(conn -> conn.getDatabase("testdb", List.of(Column.dictionary("testmap")), false, true));
 	}
 
-	private static final byte[] DUMMY_VALUE = new byte[] {0x01, 0x03};
+	private static final ByteBuf DUMMY_VALUE;
+	static {
+		ByteBuf buf = Unpooled.directBuffer(2, 2);
+		buf.writeByte(0x01);
+		buf.writeByte(0x03);
+		DUMMY_VALUE = buf;
+	}
 
 	private Flux<Entry<String, String>> addKeysAndConvertToLongerOnes(LLKeyValueDatabase db,
 			LinkedHashSet<String> originalSuperKeys,
@@ -157,7 +222,7 @@ public class Database {
 				);
 	}
 
-	private static class FixedStringSerializer implements SerializerFixedBinaryLength<String, byte[]> {
+	private static class FixedStringSerializer implements SerializerFixedBinaryLength<String, ByteBuf> {
 
 		private final int size;
 
@@ -171,13 +236,21 @@ public class Database {
 		}
 
 		@Override
-		public @NotNull String deserialize(byte @NotNull [] serialized) {
-			return new String(serialized, StandardCharsets.US_ASCII);
+		public @NotNull String deserialize(ByteBuf serialized) {
+			try {
+				return serialized.toString(StandardCharsets.US_ASCII);
+			} finally {
+				serialized.release();
+			}
 		}
 
 		@Override
-		public byte @NotNull [] serialize(@NotNull String deserialized) {
-			return deserialized.getBytes(StandardCharsets.US_ASCII);
+		public ByteBuf serialize(@NotNull String deserialized) {
+			var serialized = deserialized.getBytes(StandardCharsets.US_ASCII);
+			var serializedBuf = Unpooled.directBuffer(serialized.length, serialized.length);
+			serializedBuf.writeBytes(serialized);
+			assert serializedBuf.isDirect();
+			return serializedBuf;
 		}
 	}
 }

src/test/java/it/cavallium/dbengine/client/TestDictionaryMap.java

@@ -0,0 +1,622 @@
+package it.cavallium.dbengine.client;
+
+import static it.cavallium.dbengine.client.DbTestUtils.*;
+
+import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.UpdateMode;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+import reactor.test.StepVerifier.FirstStep;
+import reactor.test.StepVerifier.Step;
+import reactor.util.function.Tuple2;
+import reactor.util.function.Tuple3;
+import reactor.util.function.Tuple4;
+import reactor.util.function.Tuples;
+
+public class TestDictionaryMap {
+
+	private static Stream<Arguments> provideArgumentsCreate() {
+		return Arrays.stream(UpdateMode.values()).map(Arguments::of);
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsCreate")
+	public void testCreate(UpdateMode updateMode) {
+		StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.flatMap(LLDictionary::clear)
+						.then()
+				))
+				.verifyComplete();
+	}
+
+	private static Stream<Arguments> provideArgumentsPut() {
+		var goodKeys = Set.of("12345", "zebra");
+		var badKeys = Set.of("", "a", "aaaa", "aaaaaa");
+		Set<Tuple2<String, Boolean>> keys = Stream.concat(
+				goodKeys.stream().map(s -> Tuples.of(s, false)),
+				badKeys.stream().map(s -> Tuples.of(s, true))
+		).collect(Collectors.toSet());
+		var values = Set.of("a", "", "\0", "\0\0", "z", "azzszgzczqz", "bzzazazqzeztzgzzhz!");
+
+		return keys
+				.stream()
+				.flatMap(keyTuple -> {
+					Stream<String> strm;
+					if (keyTuple.getT2()) {
+						strm = values.stream().limit(1);
+					} else {
+						strm = values.stream();
+					}
+					return strm.map(val -> Tuples.of(keyTuple.getT1(), val, keyTuple.getT2()));
+				})
+				.flatMap(entryTuple -> Arrays.stream(UpdateMode.values()).map(updateMode -> Tuples.of(updateMode,
+						entryTuple.getT1(),
+						entryTuple.getT2(),
+						entryTuple.getT3()
+				)))
+				.map(fullTuple -> Arguments.of(fullTuple.getT1(), fullTuple.getT2(), fullTuple.getT3(), fullTuple.getT4()));
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testPut(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMap(map -> map
+								.putValue(key, value)
+								.then(map.getValue(null, key))
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(value).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testAtSetAtGet(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMap(map -> map
+								.at(null, key).flatMap(v -> v.set(value).doFinally(s -> v.release()))
+								.then(map.at(null, key).flatMap(v -> v.get(null).doFinally(s -> v.release())))
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(value).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testPutAndGetPrevious(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putValueAndGetPrevious(key, "error?"),
+										map.putValueAndGetPrevious(key, value),
+										map.putValueAndGetPrevious(key, value)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext("error?").expectNext(value).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testPutValueRemoveAndGetPrevious(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.removeAndGetPrevious(key),
+										map.putValue(key, value).then(map.removeAndGetPrevious(key)),
+										map.removeAndGetPrevious(key)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(value).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testPutValueRemoveAndGetStatus(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.removeAndGetStatus(key),
+										map.putValue(key, value).then(map.removeAndGetStatus(key)),
+										map.removeAndGetStatus(key)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(false, true, false).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testUpdate(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.updateValue(key, old -> {
+											assert old == null;
+											return "error?";
+										}),
+										map.updateValue(key, false, old -> {
+											assert Objects.equals(old, "error?");
+											return "error?";
+										}),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, "error?");
+											return "error?";
+										}),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, "error?");
+											return value;
+										}),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, value);
+											return value;
+										})
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (updateMode == UpdateMode.DISALLOW || shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(true, false, false, true, false).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testUpdateGet(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.updateValue(key, old -> {
+											assert old == null;
+											return "error?";
+										}).then(map.getValue(null, key)),
+										map.updateValue(key, false, old -> {
+											assert Objects.equals(old, "error?");
+											return "error?";
+										}).then(map.getValue(null, key)),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, "error?");
+											return "error?";
+										}).then(map.getValue(null, key)),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, "error?");
+											return value;
+										}).then(map.getValue(null, key)),
+										map.updateValue(key, true, old -> {
+											assert Objects.equals(old, value);
+											return value;
+										}).then(map.getValue(null, key))
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (updateMode == UpdateMode.DISALLOW || shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext("error?", "error?", "error?", value, value).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPut")
+	public void testPutAndGetStatus(UpdateMode updateMode, String key, String value, boolean shouldFail) {
+		var stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putValueAndGetStatus(key, "error?").single(),
+										map.putValueAndGetStatus(key, value).single(),
+										map.putValueAndGetStatus(key, value).single(),
+										map.remove(key),
+										map.putValueAndGetStatus(key, "error?").single()
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(false, true, true, false).verifyComplete();
+		}
+	}
+
+	private static Stream<Arguments> provideArgumentsPutMulti() {
+		var goodKeys = Set.of(Set.of("12345", "67890"), Set.of("zebra"), Set.<String>of());
+		var badKeys = Set.of(Set.of("", "12345"), Set.of("12345", "a"), Set.of("45678", "aaaa"), Set.of("aaaaaa", "capra"));
+		Set<Tuple2<Set<String>, Boolean>> keys = Stream.concat(
+				goodKeys.stream().map(s -> Tuples.of(s, false)),
+				badKeys.stream().map(s -> Tuples.of(s, true))
+		).collect(Collectors.toSet());
+		var values = Set.of("a", "", "\0", "\0\0", "z", "azzszgzczqz", "bzzazazqzeztzgzzhz!");
+
+		return keys
+				.stream()
+				.map(keyTuple -> keyTuple.mapT1(ks -> Flux
+						.zip(Flux.fromIterable(ks), Flux.fromIterable(values))
+						.collectMap(Tuple2::getT1, Tuple2::getT2)
+						.block()
+				))
+				.flatMap(entryTuple -> Arrays.stream(UpdateMode.values()).map(updateMode -> Tuples.of(updateMode,
+						entryTuple.getT1(),
+						entryTuple.getT2()
+				)))
+				.map(fullTuple -> Arguments.of(fullTuple.getT1(), fullTuple.getT2(), fullTuple.getT3()));
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiGetMulti(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map.getMulti(null, Flux.fromIterable(entries.keySet()))
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetAllValuesGetMulti(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> map
+								.setAllValues(Flux.fromIterable(entries.entrySet()))
+								.thenMany(map.getMulti(null, Flux.fromIterable(entries.keySet())))
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetAllValuesAndGetPrevious(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.setAllValuesAndGetPrevious(Flux.fromIterable(entries.entrySet())),
+										map.setAllValuesAndGetPrevious(Flux.fromIterable(entries.entrySet()))
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetGetMulti(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.set(entries).then(Mono.empty()),
+										map.getMulti(null, Flux.fromIterable(entries.keySet()))
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetAndGetStatus(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Boolean> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> {
+							Mono<Void> removalMono;
+							if (entries.isEmpty()) {
+								removalMono = Mono.empty();
+							} else {
+								removalMono = map.remove(entries.keySet().stream().findAny().orElseThrow());
+							}
+							return Flux
+									.concat(
+											map.setAndGetChanged(entries).single(),
+											map.setAndGetChanged(entries).single(),
+											removalMono.then(Mono.empty()),
+											map.setAndGetChanged(entries).single()
+									)
+									.doFinally(s -> map.release());
+						})
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			stpVer.expectNext(!entries.isEmpty(), false, !entries.isEmpty()).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetAndGetPrevious(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(map.setAndGetPrevious(entries), map.setAndGetPrevious(entries))
+								.map(Map::entrySet)
+								.flatMap(Flux::fromIterable)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testSetClearAndGetPreviousGet(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(map.set(entries).then(Mono.empty()), map.clearAndGetPrevious(), map.get(null))
+								.map(Map::entrySet)
+								.flatMap(Flux::fromIterable)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiGetAllValues(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map.getAllValues(null)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiGet(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map.get(null)
+										.map(Map::entrySet)
+										.flatMapMany(Flux::fromIterable)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiGetAllStagesGet(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Entry<String, String>> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map
+												.getAllStages(null)
+												.flatMap(stage -> stage
+														.getValue()
+														.get(null)
+														.map(val -> Map.entry(stage.getKey(), val))
+														.doFinally(s -> stage.getValue().release())
+												)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.verifyError();
+		} else {
+			entries.forEach((k, v) -> remainingEntries.add(Map.entry(k, v)));
+			for (Entry<String, String> ignored : remainingEntries) {
+				stpVer = stpVer.expectNextMatches(remainingEntries::remove);
+			}
+			stpVer.verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiIsEmpty(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Boolean> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.isEmpty(null),
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map.isEmpty(null)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.expectNext(true).verifyError();
+		} else {
+			stpVer.expectNext(true, entries.isEmpty()).verifyComplete();
+		}
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideArgumentsPutMulti")
+	public void testPutMultiClear(UpdateMode updateMode, Map<String, String> entries, boolean shouldFail) {
+		var remainingEntries = new ConcurrentHashMap<Entry<String, String>, Boolean>().keySet(true);
+		Step<Boolean> stpVer = StepVerifier
+				.create(tempDb(db -> tempDictionary(db, updateMode)
+						.map(dict -> tempDatabaseMapDictionaryMap(dict, 5))
+						.flatMapMany(map -> Flux
+								.concat(
+										map.isEmpty(null),
+										map.putMulti(Flux.fromIterable(entries.entrySet())).then(Mono.empty()),
+										map.isEmpty(null),
+										map.clear().then(Mono.empty()),
+										map.isEmpty(null)
+								)
+								.doFinally(s -> map.release())
+						)
+				));
+		if (shouldFail) {
+			stpVer.expectNext(true).verifyError();
+		} else {
+			stpVer.expectNext(true, entries.isEmpty(), true).verifyComplete();
+		}
+	}
+}

src/test/java/it/cavallium/dbengine/client/TestSingletons.java

@@ -0,0 +1,120 @@
+package it.cavallium.dbengine.client;
+
+import static it.cavallium.dbengine.client.DbTestUtils.tempDb;
+
+import it.cavallium.dbengine.database.LLKeyValueDatabase;
+import it.cavallium.dbengine.database.collections.DatabaseInt;
+import it.cavallium.dbengine.database.collections.DatabaseLong;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+public class TestSingletons {
+
+	private static Stream<Arguments> provideNumberWithRepeats() {
+		return Stream.of(
+				Arguments.of(Integer.MIN_VALUE, 2),
+				Arguments.of(-11, 2),
+				Arguments.of(0, 3),
+				Arguments.of(102, 5)
+		);
+	}
+
+	private static Stream<Arguments> provideLongNumberWithRepeats() {
+		return Stream.of(
+				Arguments.of(Long.MIN_VALUE, 2),
+				Arguments.of(-11L, 2),
+				Arguments.of(0L, 3),
+				Arguments.of(102L, 5)
+		);
+	}
+
+	@Test
+	public void testCreateInteger() {
+		StepVerifier
+				.create(tempDb(db -> tempInt(db, "test", 0)
+						.flatMap(dbInt -> dbInt.get(null))
+						.then()
+				))
+				.verifyComplete();
+	}
+
+	@Test
+	public void testCreateLong() {
+		StepVerifier
+				.create(tempDb(db -> tempLong(db, "test", 0)
+						.flatMap(dbLong -> dbLong.get(null))
+						.then()
+				))
+				.verifyComplete();
+	}
+
+	@ParameterizedTest
+	@ValueSource(ints = {Integer.MIN_VALUE, -192, -2, -1, 0, 1, 2, 1292, Integer.MAX_VALUE})
+	public void testDefaultValueInteger(int i) {
+		StepVerifier
+				.create(tempDb(db -> tempInt(db, "test", i)
+						.flatMap(dbInt -> dbInt.get(null))
+				))
+				.expectNext(i)
+				.verifyComplete();
+	}
+
+	@ParameterizedTest
+	@ValueSource(longs = {Long.MIN_VALUE, -192, -2, -1, 0, 1, 2, 1292, Long.MAX_VALUE})
+	public void testDefaultValueLong(long i) {
+		StepVerifier
+				.create(tempDb(db -> tempLong(db, "test", i)
+						.flatMap(dbLong -> dbLong.get(null))
+				))
+				.expectNext(i)
+				.verifyComplete();
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideNumberWithRepeats")
+	public void testSetInteger(Integer i, Integer repeats) {
+		StepVerifier
+				.create(tempDb(db -> tempInt(db, "test", 0)
+						.flatMap(dbInt -> Mono
+								.defer(() -> dbInt.set((int) System.currentTimeMillis()))
+								.repeat(repeats)
+								.then(dbInt.set(i))
+								.then(dbInt.get(null)))
+				))
+				.expectNext(i)
+				.verifyComplete();
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideLongNumberWithRepeats")
+	public void testSetLong(Long i, Integer repeats) {
+		StepVerifier
+				.create(tempDb(db -> tempLong(db, "test", 0)
+						.flatMap(dbLong -> Mono
+								.defer(() -> dbLong.set(System.currentTimeMillis()))
+								.repeat(repeats)
+								.then(dbLong.set(i))
+								.then(dbLong.get(null)))
+				))
+				.expectNext(i)
+				.verifyComplete();
+	}
+
+	public static Mono<DatabaseInt> tempInt(LLKeyValueDatabase database, String name, int defaultValue) {
+		return database
+				.getInteger("ints", name, defaultValue);
+	}
+
+	public static Mono<DatabaseLong> tempLong(LLKeyValueDatabase database, String name, long defaultValue) {
+		return database
+				.getLong("longs", name, defaultValue);
+	}
+}

src/test/java/it/cavallium/dbengine/database/collections/TestRanges.java

@@ -1,10 +1,21 @@
 package it.cavallium.dbengine.database.collections;
 
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.PooledByteBufAllocator;
+import io.netty.buffer.Unpooled;
+import it.cavallium.dbengine.database.LLUtils;
 import java.util.Arrays;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
+import static io.netty.buffer.Unpooled.*;
 
 public class TestRanges {
+
+	@Test
+	public void testDirectBuffer() {
+		Assertions.assertTrue(wrappedBuffer(Unpooled.directBuffer(10, 10), Unpooled.buffer(10, 10)).isDirect());
+	}
+
 	@Test
 	public void testNextRangeKey() {
 		testNextRangeKey(new byte[] {0x00, 0x00, 0x00});
@@ -21,11 +32,21 @@ public class TestRanges {
 
 	public void testNextRangeKey(byte[] prefixKey) {
 
-		byte[] firstRangeKey = DatabaseMapDictionaryDeep.firstRangeKey(prefixKey, prefixKey.length, 7, 3);
-		byte[] nextRangeKey = DatabaseMapDictionaryDeep.nextRangeKey(prefixKey, prefixKey.length, 7, 3);
+		byte[] firstRangeKey = LLUtils.toArray(DatabaseMapDictionaryDeep.firstRangeKey(PooledByteBufAllocator.DEFAULT,
+				LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(prefixKey)),
+				prefixKey.length,
+				7,
+				3
+		));
+		byte[] nextRangeKey = LLUtils.toArray(DatabaseMapDictionaryDeep.nextRangeKey(PooledByteBufAllocator.DEFAULT,
+				LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(prefixKey)),
+				prefixKey.length,
+				7,
+				3
+		));
 
 		if (Arrays.equals(prefixKey, new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF})) {
-			Assertions.assertArrayEquals(new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, nextRangeKey);
+			Assertions.assertArrayEquals(new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, 0}, nextRangeKey);
 		} else {
 			long biPrefix = 0;
 			var s = 0;
@@ -64,11 +85,23 @@ public class TestRanges {
 
 	public void testNextRangeKeyWithSuffix(byte[] prefixKey, byte[] suffixKey) {
 
-		byte[] firstRangeKey = DatabaseMapDictionaryDeep.firstRangeKey(prefixKey, suffixKey, prefixKey.length, 3, 7);
-		byte[] nextRangeKey = DatabaseMapDictionaryDeep.nextRangeKey(prefixKey, suffixKey, prefixKey.length, 3, 7);
+		byte[] firstRangeKey = LLUtils.toArray(DatabaseMapDictionaryDeep.firstRangeKey(ByteBufAllocator.DEFAULT,
+				LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(prefixKey)),
+				LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(suffixKey)),
+				prefixKey.length,
+				3,
+				7
+		));
+		byte[] nextRangeKey = LLUtils.toArray(DatabaseMapDictionaryDeep.nextRangeKey(ByteBufAllocator.DEFAULT,
+				LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(prefixKey)),
+						LLUtils.convertToDirectByteBuf(PooledByteBufAllocator.DEFAULT, wrappedBuffer(suffixKey)),
+				prefixKey.length,
+				3,
+				7
+		));
 
 		if (Arrays.equals(prefixKey, new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF}) && Arrays.equals(suffixKey, new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF})) {
-			Assertions.assertArrayEquals(new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, 0, 0, 0, 0, 0, 0, 0, 0}, nextRangeKey);
+			Assertions.assertArrayEquals(new byte[] {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, 0}, nextRangeKey);
 		} else {
 			long biPrefix = 0;
 			var s = 0;