Implement repair module, improve badBlocks function, read-only mode

pom.xml

@@ -16,7 +16,7 @@
 		<lucene.version>9.7.0</lucene.version>
     <rocksdb.version>8.5.3</rocksdb.version>
 		<junit.jupiter.version>5.9.0</junit.jupiter.version>
-    <data.generator.version>1.0.10</data.generator.version>
+    <data.generator.version>1.0.12</data.generator.version>
 	</properties>
 	<repositories>
 		<repository>
@@ -364,14 +364,6 @@
 	</dependencies>
 	<build>
 		<testSourceDirectory>src/test/java</testSourceDirectory>
-		<resources>
-			<resource>
-				<directory>../src/main/libs</directory>
-				<excludes>
-					<exclude>**/*.jar</exclude>
-				</excludes>
-			</resource>
-		</resources>
 		<extensions>
 			<extension>
 				<groupId>kr.motd.maven</groupId>
@@ -390,7 +382,7 @@
 				<artifactId>maven-compiler-plugin</artifactId>
 				<version>3.11.0</version>
 				<configuration>
-					<release>17</release>
+					<release>21</release>
           <annotationProcessorPaths>
             <annotationProcessorPath>
               <groupId>io.soabase.record-builder</groupId>
@@ -401,7 +393,9 @@
           <annotationProcessors>
             <annotationProcessor>io.soabase.recordbuilder.processor.RecordBuilderProcessor</annotationProcessor>
           </annotationProcessors>
-				</configuration>
+          <source>21</source>
+          <target>21</target>
+        </configuration>
 			</plugin>
 			<plugin>
 				<groupId>it.cavallium</groupId>
@@ -535,4 +529,80 @@
 			</plugins>
 		</pluginManagement>
 	</build>
+  <profiles>
+    <profile>
+      <id>repair</id>
+      <activation>
+        <activeByDefault>false</activeByDefault>
+        <property>
+          <name>dbengine.build</name>
+          <value>repair</value>
+        </property>
+      </activation>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>build-helper-maven-plugin</artifactId>
+            <version>3.4.0</version>
+            <executions>
+              <execution>
+                <id>add-source</id>
+                <phase>generate-sources</phase>
+                <goals>
+                  <goal>add-source</goal>
+                </goals>
+                <configuration>
+                  <sources>
+                    <source>src/repair/java</source>
+                  </sources>
+                </configuration>
+              </execution>
+            </executions>
+          </plugin>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-assembly-plugin</artifactId>
+            <version>3.6.0</version>
+            <configuration>
+              <descriptorRefs>
+                <descriptorRef>jar-with-dependencies</descriptorRef>
+              </descriptorRefs>
+              <archive>
+                <manifest>
+                  <mainClass>it.cavallium.dbengine.repair.Repair</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+            <executions>
+              <execution>
+                <id>make-assembly</id>
+                <phase>package</phase>
+                <goals>
+                  <goal>single</goal>
+                </goals>
+              </execution>
+            </executions>
+          </plugin>
+        </plugins>
+        <resources>
+          <resource>
+            <directory>src/repair/resources</directory>
+          </resource>
+        </resources>
+      </build>
+      <dependencies>
+        <dependency>
+          <groupId>org.apache.logging.log4j</groupId>
+          <artifactId>log4j-slf4j2-impl</artifactId>
+          <version>2.20.0</version>
+        </dependency>
+        <dependency>
+          <groupId>com.lmax</groupId>
+          <artifactId>disruptor</artifactId>
+          <version>3.4.4</version>
+        </dependency>
+      </dependencies>
+    </profile>
+  </profiles>
 </project>

src/main/data-generator/quic-rpc.yaml

@@ -255,6 +255,8 @@ baseTypesData:
       columnOptions: NamedColumnOptions[]
       logPath: -String
       walPath: -String
+      openAsSecondary: boolean
+      secondaryDirectoryName: -String
   # Remember to update ColumnOptions common getters
   DefaultColumnOptions:
     data:

src/main/java/it/cavallium/dbengine/client/BadBlock.java

@@ -1,8 +0,0 @@
-package it.cavallium.dbengine.client;
-
-import it.cavallium.buffer.Buf;
-import it.cavallium.dbengine.rpc.current.data.Column;
-import org.jetbrains.annotations.Nullable;
-
-public record BadBlock(String databaseName, @Nullable Column column, @Nullable Buf rawKey,
-											 @Nullable Throwable ex) {}

src/main/java/it/cavallium/dbengine/client/CompositeDatabase.java

@@ -26,7 +26,7 @@ public interface CompositeDatabase extends DatabaseProperties, DatabaseOperation
 	/**
 	 * Find corrupted items
 	 */
-	Stream<BadBlock> badBlocks();
+	Stream<VerificationProgress> verify();
 
 	void verifyChecksum();
 }

src/main/java/it/cavallium/dbengine/client/DefaultDatabaseOptions.java

@@ -66,6 +66,8 @@ public class DefaultDatabaseOptions {
 			DEFAULT_DEFAULT_COLUMN_OPTIONS,
 			List.of(),
 			NullableString.empty(),
+			NullableString.empty(),
+			false,
 			NullableString.empty()
 	);
 

src/main/java/it/cavallium/dbengine/client/VerificationProgress.java

@@ -0,0 +1,29 @@
+package it.cavallium.dbengine.client;
+
+import it.cavallium.buffer.Buf;
+import it.cavallium.dbengine.rpc.current.data.Column;
+import org.jetbrains.annotations.Nullable;
+
+public sealed interface VerificationProgress {
+	record BlockBad(String databaseName, Column column, Buf rawKey, String file, Throwable ex)
+			implements VerificationProgress {}
+	record FileOk(String databaseName, Column column, String file)
+			implements VerificationProgress {}
+	record Progress(String databaseName, Column column, String file,
+									long scanned, long total,
+									long fileScanned, long fileTotal)
+			implements VerificationProgress {
+
+		public double getProgress() {
+			return scanned / (double) total;
+		}
+
+		public double getFileProgress() {
+			return fileScanned / (double) fileTotal;
+		}
+	}
+
+	@Nullable String databaseName();
+	@Nullable Column column();
+	@Nullable String file();
+}

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

@@ -1,16 +1,14 @@
 package it.cavallium.dbengine.database;
 
 import it.cavallium.buffer.Buf;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.database.serialization.KVSerializationFunction;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
-import java.io.IOException;
 import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Stream;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.rocksdb.RocksDBException;
 
 @SuppressWarnings("unused")
 public interface LLDictionary extends LLKeyValueDatabaseStructure {
@@ -66,7 +64,7 @@ public interface LLDictionary extends LLKeyValueDatabaseStructure {
 			int prefixLength,
 			boolean smallRange);
 
-	Stream<BadBlock> badBlocks(LLRange range);
+	Stream<VerificationProgress> badBlocks(LLRange range);
 
 	void setRange(LLRange range, Stream<LLEntry> entries, boolean smallRange);
 

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

@@ -1,6 +1,8 @@
 package it.cavallium.dbengine.database;
 
 import it.cavallium.buffer.Buf;
+import it.cavallium.dbengine.database.disk.LiveFileMetadata;
+import java.util.Objects;
 import java.util.StringJoiner;
 import org.jetbrains.annotations.Nullable;
 
@@ -19,6 +21,8 @@ public class LLRange {
 
 	private LLRange(@Nullable Buf min, @Nullable Buf max, @Nullable Buf single) {
 		assert single == null || (min == null && max == null);
+		assert min == null || max == null || min.compareTo(max) <= 0
+				: "Minimum buffer is bigger than maximum buffer: " + min + " > " + max;
 		this.min = min;
 		this.max = max;
 		this.single = single;
@@ -44,6 +48,57 @@ public class LLRange {
 		return new LLRange(min, max, null);
 	}
 
+	public static boolean isInside(LLRange rangeSub, LLRange rangeParent) {
+		if (rangeParent.isAll()) {
+			return true;
+		} else if (rangeParent.isSingle()) {
+			return Objects.equals(rangeSub, rangeParent);
+		} else {
+			return ((!rangeParent.hasMin() || (rangeSub.hasMin() && rangeParent.getMin().compareTo(rangeSub.getMin()) <= 0)))
+					&& ((!rangeParent.hasMax() || (rangeSub.hasMax() && rangeParent.getMax().compareTo(rangeSub.getMax()) >= 0)));
+		}
+	}
+
+	@Nullable
+	public static LLRange intersect(LLRange rangeA, LLRange rangeB) {
+		boolean aEndInclusive = rangeA.isSingle();
+		boolean bEndInclusive = rangeB.isSingle();
+		Buf min = rangeA.isAll()
+				? rangeB.getMin()
+				: (rangeB.isAll()
+						? rangeA.getMin()
+						: (rangeA.getMin().compareTo(rangeB.getMin()) <= 0 ? rangeB.getMin() : rangeA.getMin()));
+		int aComparedToB;
+		Buf max;
+		boolean maxInclusive;
+		if (rangeA.isAll()) {
+			max = rangeB.getMax();
+			maxInclusive = bEndInclusive;
+		} else if (rangeB.isAll()) {
+			max = rangeA.getMax();
+			maxInclusive = aEndInclusive;
+		} else if ((aComparedToB = rangeA.getMax().compareTo(rangeB.getMax())) >= 0) {
+			max = rangeB.getMax();
+			if (aComparedToB == 0) {
+				maxInclusive = bEndInclusive && aEndInclusive;
+			} else {
+				maxInclusive = bEndInclusive;
+			}
+		} else {
+			max = rangeA.getMax();
+			maxInclusive = aEndInclusive;
+		}
+		if (min != null && max != null && min.compareTo(max) >= (maxInclusive ? 1 : 0)) {
+			return null;
+		} else {
+			if (min != null && min.equals(max)) {
+				return LLRange.single(min);
+			} else {
+				return LLRange.of(min, max);
+			}
+		}
+	}
+
 	public boolean isAll() {
 		return min == null && max == null && single == null;
 	}
@@ -108,12 +163,20 @@ public class LLRange {
 		return result;
 	}
 
+	@SuppressWarnings("UnnecessaryUnicodeEscape")
 	@Override
 	public String toString() {
-		return new StringJoiner(", ", LLRange.class.getSimpleName() + "[", "]")
-				.add("min=" + LLUtils.toString(min))
-				.add("max=" + LLUtils.toString(max))
-				.toString();
+		if (single != null) {
+			return "[" + single + "]";
+		} else if (min != null && max != null) {
+			return "[" + LLUtils.toString(min) + "," + LLUtils.toString(max) + ")";
+		} else if (min != null) {
+			return "[" + min + ",\u221E)";
+		} else if (max != null) {
+			return "[\u2205," + max + ")";
+		} else {
+			return "[\u221E)";
+		}
 	}
 
 	public LLRange copy() {

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

@@ -91,7 +91,7 @@ public class LLUtils {
 	private static final Consumer<Object> NULL_CONSUMER = ignored -> {};
 	private static final Buf BUF_TRUE = Buf.wrap(new byte[] {(byte) 1});
 	private static final Buf BUF_FALSE = Buf.wrap(new byte[] {(byte) 0});
-	private static final HexFormat HEX_FORMAT = HexFormat.of().withUpperCase();
+	public static final HexFormat HEX_FORMAT = HexFormat.of().withUpperCase();
 
 	static {
 		for (int i1 = 0; i1 < 256; i1++) {
@@ -487,7 +487,7 @@ public class LLUtils {
 			}
 		}
 		readOptions.setFillCache(canFillCache && !hugeRange);
-		readOptions.setVerifyChecksums(!FORCE_DISABLE_CHECKSUM_VERIFICATION && !hugeRange);
+		readOptions.setVerifyChecksums(!FORCE_DISABLE_CHECKSUM_VERIFICATION || !hugeRange);
 
 		return readOptions;
 	}

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

@@ -5,7 +5,7 @@ import static it.cavallium.dbengine.utils.StreamUtils.resourceStream;
 import it.cavallium.buffer.Buf;
 import it.cavallium.buffer.BufDataInput;
 import it.cavallium.buffer.BufDataOutput;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.LLDictionaryResultType;
@@ -18,7 +18,6 @@ import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
 import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.Serializer;
 import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
-import it.cavallium.dbengine.utils.StreamUtils;
 import it.unimi.dsi.fastutil.objects.Object2ObjectSortedMap;
 import java.util.Map.Entry;
 import java.util.Optional;
@@ -270,7 +269,7 @@ public class DatabaseMapDictionaryDeep<T, U, US extends DatabaseStage<U>> implem
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return dictionary.badBlocks(range);
 	}
 

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

@@ -1,7 +1,7 @@
 package it.cavallium.dbengine.database.collections;
 
 import it.cavallium.buffer.Buf;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.SubStageEntry;
@@ -148,7 +148,7 @@ public class DatabaseMapDictionaryHashed<T, U, TH> implements DatabaseStageMap<T
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return this.subDictionary.badBlocks();
 	}
 

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

@@ -3,7 +3,7 @@ package it.cavallium.dbengine.database.collections;
 import it.cavallium.buffer.Buf;
 import it.cavallium.buffer.BufDataInput;
 import it.cavallium.buffer.BufDataOutput;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.Delta;
 import it.cavallium.dbengine.database.LLDictionary;
@@ -121,7 +121,7 @@ public final class DatabaseMapSingle<U> implements DatabaseStageEntry<U> {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return dictionary.badBlocks(LLRange.single(key));
 	}
 

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

@@ -1,6 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.Delta;
 import it.cavallium.dbengine.database.LLUtils;
@@ -124,7 +124,7 @@ public class DatabaseSingleBucket<K, V, TH> implements DatabaseStageEntry<V> {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return bucketStage.badBlocks();
 	}
 

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

@@ -1,6 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.client.Mapper;
 import it.cavallium.dbengine.database.Delta;
@@ -107,7 +107,7 @@ public class DatabaseSingleMapped<A, B> implements DatabaseStageEntry<A> {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return this.serializedSingle.badBlocks();
 	}
 

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

@@ -3,7 +3,7 @@ package it.cavallium.dbengine.database.collections;
 import it.cavallium.buffer.Buf;
 import it.cavallium.buffer.BufDataInput;
 import it.cavallium.buffer.BufDataOutput;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.Delta;
 import it.cavallium.dbengine.database.LLSingleton;
@@ -119,7 +119,7 @@ public class DatabaseSingleton<U> implements DatabaseStageEntry<U> {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks() {
+	public Stream<VerificationProgress> badBlocks() {
 		return Stream.empty();
 	}
 }

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

@@ -1,6 +1,6 @@
 package it.cavallium.dbengine.database.collections;
 
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.client.CompositeSnapshot;
 import it.cavallium.dbengine.database.Delta;
 import it.cavallium.dbengine.database.LLUtils;
@@ -64,5 +64,5 @@ public interface DatabaseStage<T> extends DatabaseStageWithEntry<T> {
 		return leavesCount(snapshot, false) <= 0;
 	}
 
-	Stream<BadBlock> badBlocks();
+	Stream<VerificationProgress> badBlocks();
 }

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

@@ -7,6 +7,7 @@ import io.micrometer.core.instrument.DistributionSummary;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Timer;
 import it.cavallium.buffer.Buf;
+import it.cavallium.dbengine.database.ColumnUtils;
 import it.cavallium.dbengine.database.LLRange;
 import it.cavallium.dbengine.database.LLUtils;
 import it.cavallium.dbengine.database.RepeatedElementList;
@@ -18,10 +19,12 @@ import it.cavallium.dbengine.database.serialization.SerializationFunction;
 import it.cavallium.dbengine.utils.SimpleResource;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.StampedLock;
+import java.util.stream.Stream;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.jetbrains.annotations.NotNull;
@@ -32,6 +35,7 @@ import org.rocksdb.CompactRangeOptions;
 import org.rocksdb.FlushOptions;
 import org.rocksdb.Holder;
 import org.rocksdb.KeyMayExist;
+import org.rocksdb.LiveFileMetaData;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksDBException;
 import org.rocksdb.RocksObject;
@@ -555,6 +559,15 @@ public sealed abstract class AbstractRocksDBColumn<T extends RocksDB> implements
 		}
 	}
 
+	@Override
+	public Stream<LiveFileMetadata> getAllLiveFiles() throws RocksDBException {
+		byte[] cfhName = cfh.getName();
+		return db.getLiveFilesMetaData().stream()
+				.filter(file -> Arrays.equals(cfhName, file.columnFamilyName()))
+				.map(file -> new LiveFileMetadata(file.path(), file.fileName(), file.level(), columnName,
+						file.numEntries(),file.size(), LLRange.of(Buf.wrap(file.smallestKey()), Buf.wrap(file.largestKey()))));
+	}
+
 	protected int getLevels() {
 		var closeReadLock = closeLock.readLock();
 		try {

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

@@ -60,13 +60,17 @@ public class LLLocalDatabaseConnection implements LLDatabaseConnection {
 		return new LLLocalKeyValueDatabase(meterRegistry,
 				name,
 				inMemory,
-				basePath.resolve("database_" + name),
+				getDatabasePath(name),
 				columns,
 				new LinkedList<>(),
 				databaseOptions
 		);
 	}
 
+	public Path getDatabasePath(String databaseName) {
+		return basePath.resolve("database_" + databaseName);
+	}
+
 	@Override
 	public LLLuceneIndex getLuceneIndex(String clusterName,
 			LuceneIndexStructure indexStructure,

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

@@ -4,7 +4,6 @@ import static it.cavallium.dbengine.database.LLUtils.MARKER_ROCKSDB;
 import static it.cavallium.dbengine.database.LLUtils.isBoundedRange;
 import static it.cavallium.dbengine.database.LLUtils.mapList;
 import static it.cavallium.dbengine.database.LLUtils.toStringSafe;
-import static it.cavallium.dbengine.database.LLUtils.wrapNullable;
 import static it.cavallium.dbengine.database.disk.UpdateAtomicResultMode.DELTA;
 import static it.cavallium.dbengine.utils.StreamUtils.ROCKSDB_POOL;
 import static it.cavallium.dbengine.utils.StreamUtils.collectOn;
@@ -18,7 +17,10 @@ import static it.cavallium.dbengine.utils.StreamUtils.batches;
 import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.Timer;
 import it.cavallium.buffer.Buf;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
+import it.cavallium.dbengine.client.VerificationProgress.BlockBad;
+import it.cavallium.dbengine.client.VerificationProgress.FileOk;
+import it.cavallium.dbengine.client.VerificationProgress.Progress;
 import it.cavallium.dbengine.database.ColumnUtils;
 import it.cavallium.dbengine.database.LLDelta;
 import it.cavallium.dbengine.database.LLDictionary;
@@ -36,19 +38,26 @@ import it.cavallium.dbengine.database.disk.rocksdb.LLReadOptions;
 import it.cavallium.dbengine.database.disk.rocksdb.LLWriteOptions;
 import it.cavallium.dbengine.database.serialization.KVSerializationFunction;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
-import it.cavallium.dbengine.rpc.current.data.DatabaseOptions;
+import it.cavallium.dbengine.rpc.current.data.Column;
 import it.cavallium.dbengine.utils.DBException;
+import it.cavallium.dbengine.utils.StreamUtils;
 import java.io.IOException;
-import java.nio.ByteBuffer;
+import java.math.BigInteger;
+import java.nio.file.Path;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.CompletionException;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.LongAdder;
 import java.util.function.Function;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
-import org.apache.commons.lang3.tuple.Pair;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.util.Supplier;
@@ -628,38 +637,95 @@ public class LLLocalDictionary implements LLDictionary {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks(LLRange range) {
+	public Stream<VerificationProgress> badBlocks(LLRange rangeFull) {
+		Set<String> brokenFiles = new ConcurrentHashMap<String, Boolean>().keySet(true);
+		LongAdder totalScanned = new LongAdder();
+		AtomicLong totalEstimate = new AtomicLong();
+
 		try {
-			return resourceStream(
-					() -> LLUtils.generateCustomReadOptions(null, false, isBoundedRange(range), false),
-					ro -> {
-				ro.setFillCache(false);
-				if (!range.isSingle()) {
-					if (LLUtils.MANUAL_READAHEAD) {
-						ro.setReadaheadSize(32 * 1024);
-					}
-				}
-				ro.setVerifyChecksums(true);
-				return resourceStream(() ->  db.newRocksIterator(ro, range, false), rocksIterator -> {
-					rocksIterator.seekToFirst();
-					return streamWhileNonNull(() -> {
-						if (!rocksIterator.isValid()) return null;
-						Buf rawKey = null;
+			totalEstimate.set(db.getNumEntries());
+		} catch (Throwable ex) {
+			logger.warn("Failed to get total entries count", ex);
+		}
+
+		Column column = ColumnUtils.special(columnName);
+		try {
+			record FileRange(String path, @Nullable LLRange range, long countEstimate) {}
+
+			return db.getAllLiveFiles()
+					.map(metadata -> new FileRange(Path.of(metadata.path()).resolve("./" + metadata.fileName()).normalize().toString(),
+							LLRange.intersect(metadata.keysRange(), rangeFull),
+							metadata.numEntries()
+					))
+					.filter(fr -> fr.range != null)
+					.parallel()
+					.<VerificationProgress>flatMap(fr -> {
+						String path = fr.path;
+						LLRange rangePartial = fr.range;
+						AtomicLong fileScanned = new AtomicLong();
+						final long fileEstimate = fr.countEstimate;
+						AtomicBoolean streamEnded = new AtomicBoolean(false);
+						totalScanned.add(fileEstimate);
 						try {
-							rawKey = rocksIterator.keyBuf().copy();
-							rocksIterator.next();
-						} catch (RocksDBException ex) {
-							return new BadBlock(databaseName, ColumnUtils.special(columnName), rawKey, ex);
+							return resourceStream(
+									() -> LLUtils.generateCustomReadOptions(null, false, isBoundedRange(rangePartial), false),
+									ro -> {
+										ro.setFillCache(false);
+										if (!rangePartial.isSingle()) {
+											if (LLUtils.MANUAL_READAHEAD) {
+												ro.setReadaheadSize(32 * 1024);
+											}
+										}
+										ro.setVerifyChecksums(true);
+										return resourceStream(() -> db.newRocksIterator(ro, rangePartial, false), rocksIterator -> {
+											rocksIterator.seekToFirst();
+											return StreamUtils.<Optional<VerificationProgress>>streamWhileNonNull(() -> {
+												if (!rocksIterator.isValid()) {
+													if (streamEnded.compareAndSet(false, true)) {
+														totalScanned.add(fileScanned.get() - fileEstimate);
+														return Optional.of(new FileOk(databaseName, column, path));
+													} else {
+														//noinspection OptionalAssignedToNull
+														return null;
+													}
+												}
+												boolean shouldSendStatus;
+												Buf rawKey = null;
+												try {
+													rawKey = rocksIterator.keyBuf().copy();
+													shouldSendStatus = fileScanned.incrementAndGet() % 1_000_000 == 0;
+													rocksIterator.next();
+												} catch (RocksDBException ex) {
+													return Optional.of(new BlockBad(databaseName, column, rawKey, path, ex));
+												}
+												if (shouldSendStatus) {
+													long totalScannedValue = totalScanned.sum();
+													long fileScannedVal = fileScanned.get();
+													return Optional.of(new Progress(databaseName,
+															column,
+															path,
+															totalScannedValue,
+															Math.max(totalEstimate.get(), totalScannedValue),
+															fileScannedVal,
+															Math.max(fileEstimate, fileScannedVal)
+													));
+												} else {
+													return Optional.empty();
+												}
+											}).filter(Optional::isPresent).map(Optional::get).onClose(() -> {
+												rocksIterator.close();
+												ro.close();
+											});
+										});
+									}
+							);
+						} catch (RocksDBException e) {
+							return Stream.of(new BlockBad(databaseName, column, null, path, e));
 						}
-						return null;
-					}).takeWhile(x -> rocksIterator.isValid()).onClose(() -> {
-						rocksIterator.close();
-						ro.close();
-					});
-				});
-			});
+					})
+					.filter(err -> !(err instanceof BlockBad blockBad && blockBad.rawKey() == null && !brokenFiles.add(blockBad.file())));
 		} catch (RocksDBException e) {
-			throw new DBException("Failed to get bad blocks", e);
+			return Stream.of(new BlockBad(databaseName, column, null, null, e));
 		}
 	}
 
@@ -1011,6 +1077,95 @@ public class LLLocalDictionary implements LLDictionary {
 		}
 	}
 
+	private static BigInteger getRangePointAt(LLRange range,
+			BigInteger minBi,
+			BigInteger maxBi,
+			BigInteger rangeBi,
+			int pointsCount,
+			BigInteger pointsCountBi,
+			int i) {
+		if (i == 0) {
+			return range.hasMin() ? minBi : null;
+		} else if (i + 1 == pointsCount) {
+			return range.hasMax() ? maxBi : null;
+		} else {
+			return minBi.add(rangeBi.multiply(BigInteger.valueOf(i)).divide(pointsCountBi));
+		}
+	}
+
+	private static Buf getMinBufForParallelization(LLRange range) {
+		Buf min = range.getMin();
+		if (min != null) {
+			return min;
+		} else {
+			return Buf.wrap();
+		}
+	}
+
+	private static Buf getMaxBufForParallelization(LLRange range) {
+		Buf max = range.getMax();
+		if (max != null) {
+			return max;
+		} else {
+			max = range.getMin().copy();
+			max.add(Byte.MAX_VALUE);
+			return max.freeze();
+		}
+	}
+
+	public static Stream<LLRange> parallelizeRange(LLRange range) {
+		return parallelizeRange(range, Math.max(Runtime.getRuntime().availableProcessors() - 1, 1));
+	}
+
+	public static Stream<LLRange> parallelizeRange(LLRange range, int threads) {
+		if (threads < 1) {
+			throw new IllegalArgumentException();
+		}
+		if (range.isAll()) {
+			return IntStream
+					.range(-1, LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS.length)
+					.mapToObj(idx -> LLRange.of(
+							Buf.wrap(idx == -1 ? new byte[0] : LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS[idx]),
+							idx + 1 >= LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS.length ? null : Buf.wrap(LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS[idx + 1])));
+		} else if (range.isSingle()) {
+			return Stream.of(range);
+		} else {
+			Buf minBuf = getMinBufForParallelization(range);
+			Buf maxBuf = getMaxBufForParallelization(range);
+			byte[] minUnboundedArray = minBuf.asUnboundedArray();
+			byte[] maxUnboundedArray = maxBuf.asUnboundedArray();
+			var minBi = minBuf.isEmpty() ? BigInteger.ZERO : new BigInteger(minUnboundedArray, 0, minBuf.size());
+			var maxBi = new BigInteger(maxUnboundedArray, 0, maxBuf.size());
+			BigInteger rangeBi = maxBi.subtract(minBi);
+			int pointsCount = rangeBi.min(BigInteger.valueOf(threads).add(BigInteger.ONE)).intValueExact();
+			int segmentsCount = pointsCount - 1;
+			if (threads > 2 && segmentsCount <= 2) {
+				return Stream.of(range);
+			}
+			BigInteger pointsCountBi = BigInteger.valueOf(pointsCount);
+
+			byte[][] points = new byte[pointsCount][];
+			for (int i = 0; i < pointsCount; i++) {
+				BigInteger rangePoint = getRangePointAt(range, minBi, maxBi, rangeBi, pointsCount, pointsCountBi, i);
+				points[i] = rangePoint != null ? rangePoint.toByteArray() : null;
+			}
+
+			LLRange[] ranges = new LLRange[segmentsCount];
+			for (int i = 0; i < segmentsCount; i++) {
+				byte[] min = points[i];
+				byte[] max = points[i + 1];
+				if (min == null) {
+					ranges[i] = LLRange.to(Buf.wrap(max));
+				} else if (max == null) {
+					ranges[i] = LLRange.from(Buf.wrap(min));
+				} else {
+					ranges[i] = LLRange.of(Buf.wrap(min), Buf.wrap(max));
+				}
+			}
+			return Stream.of(ranges);
+		}
+	}
+
 	private long exactSizeAll(@Nullable LLSnapshot snapshot) {
 		if (LLUtils.isInNonBlockingThread()) {
 			throw new UnsupportedOperationException("Called exactSizeAll in a nonblocking thread");
@@ -1022,19 +1177,11 @@ public class LLLocalDictionary implements LLDictionary {
 			readOpts.setVerifyChecksums(VERIFY_CHECKSUMS_WHEN_NOT_NEEDED);
 
 			if (PARALLEL_EXACT_SIZE) {
-				return collectOn(ROCKSDB_POOL, IntStream
-						.range(-1, LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS.length)
-						.mapToObj(idx -> Pair.of(idx == -1 ? new byte[0] : LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS[idx],
-								idx + 1 >= LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS.length ? null
-										: LLUtils.LEXICONOGRAPHIC_ITERATION_SEEKS[idx + 1]
-						)).map(range -> {
+				return collectOn(ROCKSDB_POOL, parallelizeRange(LLRange.all()).map(range -> {
 							long partialCount = 0;
 							try (var rangeReadOpts = readOpts.copy()) {
 								try {
-									try (var rocksIterator = db.newIterator(rangeReadOpts,
-											wrapNullable(range.getKey()),
-											wrapNullable(range.getValue())
-									)) {
+									try (var rocksIterator = db.newRocksIterator(rangeReadOpts, range, false)) {
 										rocksIterator.seekToFirst();
 										while (rocksIterator.isValid()) {
 											partialCount++;

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

@@ -34,6 +34,7 @@ import it.cavallium.dbengine.rpc.current.data.NoFilter;
 import java.io.File;
 import java.io.IOException;
 import it.cavallium.dbengine.utils.DBException;
+import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -45,6 +46,7 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ThreadLocalRandom;
@@ -425,7 +427,23 @@ public class LLLocalKeyValueDatabase extends Backuppable implements LLKeyValueDa
 			while (true) {
 				try {
 					// a factory method that returns a RocksDB instance
-					if (databaseOptions.optimistic()) {
+					if (databaseOptions.openAsSecondary()) {
+						var secondaryPath = dbPath
+								.resolve("secondary-log")
+								.resolve(databaseOptions.secondaryDirectoryName().orElse("unnamed-" + UUID.randomUUID()));
+						try {
+							Files.createDirectories(secondaryPath);
+						} catch (IOException e) {
+							throw new RocksDBException("Failed to create secondary exception: " + e);
+						}
+						this.db = RocksDB.openAsSecondary(rocksdbOptions,
+								dbPathString,
+								secondaryPath
+										.toString(),
+								descriptors,
+								handles
+						);
+					} else if (databaseOptions.optimistic()) {
 						this.db = OptimisticTransactionDB.open(rocksdbOptions, dbPathString, descriptors, handles);
 					} else {
 						var transactionOptions = new TransactionDBOptions()
@@ -475,7 +493,10 @@ public class LLLocalKeyValueDatabase extends Backuppable implements LLKeyValueDa
 			handles.forEach(refs::track);
 
 			// compactDb(db, handles);
-			flushDb(db, handles);
+			if (!databaseOptions.openAsSecondary()) {
+				logger.info("Flushing database at {}", dbPathString);
+				flushDb(db, handles);
+			}
 		} catch (RocksDBException ex) {
 			throw new DBException(ex);
 		}

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

@@ -0,0 +1,8 @@
+package it.cavallium.dbengine.database.disk;
+
+import it.cavallium.dbengine.database.LLRange;
+
+public record LiveFileMetadata(String path, String fileName, int level, String columnName, long numEntries, long size,
+															 LLRange keysRange) {
+	
+}

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

@@ -10,6 +10,7 @@ import it.cavallium.dbengine.database.disk.rocksdb.RocksIteratorObj;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
 import java.io.IOException;
 import java.util.List;
+import java.util.stream.Stream;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.rocksdb.ColumnFamilyHandle;
@@ -53,6 +54,8 @@ public sealed interface RocksDBColumn permits AbstractRocksDBColumn {
 
 	@NotNull RocksIteratorObj newIterator(@NotNull LLReadOptions readOptions, @Nullable Buf min, @Nullable Buf max);
 
+	Stream<LiveFileMetadata> getAllLiveFiles() throws RocksDBException;
+
 	@NotNull UpdateAtomicResult updateAtomic(@NotNull LLReadOptions readOptions,
 			@NotNull LLWriteOptions writeOptions,
 			Buf key,

src/main/java/it/cavallium/dbengine/database/disk/rocksdb/LLReadOptions.java

@@ -2,8 +2,11 @@ package it.cavallium.dbengine.database.disk.rocksdb;
 
 import it.cavallium.dbengine.database.disk.IteratorMetrics;
 import it.cavallium.dbengine.utils.SimpleResource;
+import java.util.Arrays;
 import org.rocksdb.ColumnFamilyHandle;
+import org.rocksdb.LiveFileMetaData;
 import org.rocksdb.ReadOptions;
+import org.rocksdb.ReadTier;
 import org.rocksdb.RocksDB;
 import org.rocksdb.Snapshot;
 

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

@@ -5,7 +5,7 @@ import static java.util.stream.Collectors.groupingBy;
 import static java.util.stream.Collectors.mapping;
 
 import it.cavallium.buffer.Buf;
-import it.cavallium.dbengine.client.BadBlock;
+import it.cavallium.dbengine.client.VerificationProgress;
 import it.cavallium.dbengine.database.LLDelta;
 import it.cavallium.dbengine.database.LLDictionary;
 import it.cavallium.dbengine.database.LLDictionaryResultType;
@@ -19,14 +19,11 @@ import it.cavallium.dbengine.database.UpdateMode;
 import it.cavallium.dbengine.database.serialization.KVSerializationFunction;
 import it.cavallium.dbengine.database.serialization.SerializationException;
 import it.cavallium.dbengine.database.serialization.SerializationFunction;
-import it.cavallium.dbengine.utils.DBException;
-import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Set;
-import java.util.SortedMap;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentNavigableMap;
 import java.util.concurrent.ConcurrentSkipListMap;
@@ -361,7 +358,7 @@ public class LLMemoryDictionary implements LLDictionary {
 	}
 
 	@Override
-	public Stream<BadBlock> badBlocks(LLRange range) {
+	public Stream<VerificationProgress> badBlocks(LLRange range) {
 		return Stream.empty();
 	}
 

src/repair/java/it/cavallium/dbengine/repair/Repair.java

@@ -0,0 +1,248 @@
+package it.cavallium.dbengine.repair;
+
+import io.micrometer.core.instrument.Clock;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.logging.LoggingMeterRegistry;
+import it.cavallium.datagen.nativedata.NullableString;
+import it.cavallium.datagen.nativedata.Nullableboolean;
+import it.cavallium.datagen.nativedata.Nullableint;
+import it.cavallium.datagen.nativedata.Nullablelong;
+import it.cavallium.dbengine.client.VerificationProgress.BlockBad;
+import it.cavallium.dbengine.client.VerificationProgress.FileOk;
+import it.cavallium.dbengine.client.VerificationProgress.Progress;
+import it.cavallium.dbengine.database.LLRange;
+import it.cavallium.dbengine.database.UpdateMode;
+import it.cavallium.dbengine.database.disk.LLLocalDatabaseConnection;
+import it.cavallium.dbengine.database.disk.LLLocalDictionary;
+import it.cavallium.dbengine.database.disk.LLLocalKeyValueDatabase;
+import it.cavallium.dbengine.rpc.current.data.Column;
+import it.cavallium.dbengine.rpc.current.data.DatabaseOptionsBuilder;
+import it.cavallium.dbengine.rpc.current.data.DatabaseVolume;
+import it.cavallium.dbengine.rpc.current.data.DefaultColumnOptions;
+import it.cavallium.dbengine.rpc.current.data.NamedColumnOptions;
+import it.cavallium.dbengine.rpc.current.data.nullables.NullableCompression;
+import it.cavallium.dbengine.rpc.current.data.nullables.NullableFilter;
+import it.cavallium.dbengine.utils.StreamUtils;
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
+import it.unimi.dsi.fastutil.objects.ObjectList;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Base64;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.stream.Stream;
+import org.rocksdb.Options;
+import org.rocksdb.RocksDB;
+import org.rocksdb.RocksDBException;
+
+public class Repair {
+
+	public static final MeterRegistry METER = LoggingMeterRegistry
+			.builder(key -> null)
+			.clock(Clock.SYSTEM)
+			.loggingSink(System.err::println)
+			.build();
+
+	public static void main(String[] argsArray) throws RocksDBException {
+		ObjectList<String> initialArgs = ObjectArrayList.wrap(argsArray), args = initialArgs;
+		if (args.isEmpty() || args.contains("--help")) {
+			printHelp(initialArgs);
+		}
+		String command = args.get(0);
+		args = args.subList(1, args.size());
+		switch (command.toLowerCase(Locale.ROOT)) {
+			case "list-column-families" -> {
+				if (args.size() < 3) {
+					printHelp(initialArgs);
+				}
+				Path path = Path.of(args.get(0));
+				String dbName = args.get(1);
+				getColumnFamilyNames(path, dbName).forEach(s -> System.err.printf("\tColumn family: %s%n", s));
+			}
+			case "scan-all" -> {
+				if (args.size() < 2) {
+					printHelp(initialArgs);
+				}
+				Path path = Path.of(args.get(0)).toAbsolutePath();
+				String dbName = args.get(1);
+				List<String> columnNames = args.size() < 3 ? getColumnFamilyNames(path, dbName).toList() : args.subList(2, args.size());
+				System.err.printf("Scanning database \"%s\" at \"%s\", column families to scan:\n\t%s%n", dbName, path, String.join("\n\t", columnNames));
+				var conn = new LLLocalDatabaseConnection(METER, path, false);
+				conn.connect();
+				LLLocalKeyValueDatabase db = getDatabase(conn, dbName, columnNames);
+				db.getAllColumnFamilyHandles().forEach((column, cfh) -> {
+					System.err.printf("Scanning column: %s%n", column.name());
+					LLLocalDictionary dict = db.getDictionary(column.name().getBytes(StandardCharsets.UTF_8), UpdateMode.DISALLOW);
+					StreamUtils.collectOn(StreamUtils.ROCKSDB_POOL, dict.badBlocks(LLRange.all()), StreamUtils.executing(block -> {
+						synchronized (Repair.class) {
+							switch (block) {
+								case null -> {}
+								case BlockBad blockBad -> {
+									System.err.println("[ ! ] Bad block found: " + block.databaseName() + (block.column() != null ? "->" + block.column().name() : "") + "->" + blockBad.rawKey() + "->" + block.file());
+									if (blockBad.ex() != null) {
+										if (blockBad.ex() instanceof RocksDBException ex) {
+											System.err.println("\t" + ex);
+										} else {
+											blockBad.ex().printStackTrace(System.err);
+										}
+									}
+								}
+								case FileOk fileOk -> {
+									System.err.println("File is ok: " + block.databaseName() + (block.column() != null ? "->" + block.column().name() : "") + "->" + block.file());
+								}
+								case Progress progress -> {
+									System.err.printf("Progress: [%d/%d] file: [%d/%d] %s->%s->%s%n",
+											progress.scanned(),
+											progress.total(),
+											progress.fileScanned(),
+											progress.fileTotal(),
+											block.databaseName(),
+											block.column() != null ? "->" + block.column().name() : "",
+											block.file()
+									);
+								}
+								default -> throw new IllegalStateException("Unexpected value: " + block);
+							}
+						}
+					}));
+				});
+			}
+			case "dump-all" -> {
+				if (args.size() < 2) {
+					printHelp(initialArgs);
+				}
+				Path path = Path.of(args.get(0)).toAbsolutePath();
+				String dbName = args.get(1);
+				List<String> columnNames = args.size() < 3 ? getColumnFamilyNames(path, dbName).toList() : args.subList(2, args.size());
+				System.err.printf("Dumping database \"%s\" at \"%s\", column families to dump:\n\t%s%n", dbName, path, String.join("\n\t", columnNames));
+				var conn = new LLLocalDatabaseConnection(METER, path, false);
+				conn.connect();
+				LLLocalKeyValueDatabase db = getDatabase(conn, dbName, columnNames);
+				System.out.println("{\"columns\": {");
+				AtomicBoolean first = new AtomicBoolean(true);
+				db.getAllColumnFamilyHandles().forEach((column, cfh) -> {
+					if (!first.compareAndSet(true, false)) {
+						System.out.println(",");
+					}
+					System.out.printf("\"%s\": [", column.name());
+					System.err.printf("Dumping column: %s%n", column.name());
+					AtomicBoolean firstElem = new AtomicBoolean(true);
+					var dict = db.getDictionary(column.name().getBytes(StandardCharsets.UTF_8), UpdateMode.DISALLOW);
+					dict.getRange(null, LLRange.all(), false, false).forEach(elem -> {
+						if (!firstElem.compareAndSet(true, false)) {
+							System.out.println(",");
+						} else {
+							System.out.println();
+						}
+						System.out.printf("{\"key\": \"%s\", \"value\": \"%s\"}",
+								Base64.getEncoder().encodeToString(elem.getKey().toByteArray()),
+								Base64.getEncoder().encodeToString(elem.getValue().toByteArray())
+						);
+						System.err.printf("\t\tkey: %s\tvalue: %s%n", elem.getKey().toString(), elem.getValue().toString(StandardCharsets.UTF_8));
+					});
+					System.out.printf("%n]");
+				});
+				System.out.println();
+				System.out.println("}");
+				System.out.println("}");
+			}
+			case "verify-checksum" -> {
+				if (args.size() != 2) {
+					printHelp(initialArgs);
+				}
+				Path path = Path.of(args.get(0)).toAbsolutePath();
+				String dbName = args.get(1);
+				List<String> columnNames = getColumnFamilyNames(path, dbName).toList();
+				System.err.printf("Verifying checksum of database \"%s\" at \"%s\", column families:\n\t%s%n", dbName, path, String.join("\n\t", columnNames));
+				var conn = new LLLocalDatabaseConnection(METER, path, false);
+				conn.connect();
+				LLLocalKeyValueDatabase db = getDatabase(conn, dbName, columnNames);
+				db.verifyChecksum();
+				System.err.println("Done");
+			}
+			default -> printHelp(initialArgs);
+		}
+		System.exit(0);
+	}
+
+	private static Stream<String> getColumnFamilyNames(Path path, String dbName) throws RocksDBException {
+		String dbPath = path.resolve("database_" + dbName).toString();
+		System.err.printf("Listing column families of database: %s%n", dbPath);
+		try (var options = new Options()) {
+			options.setCreateIfMissing(false).setCreateMissingColumnFamilies(false);
+			return RocksDB.listColumnFamilies(options, dbPath).stream().map(s -> new String(s, StandardCharsets.UTF_8));
+		}
+	}
+
+	private static LLLocalKeyValueDatabase getDatabase(LLLocalDatabaseConnection conn,
+			String dbName,
+			List<String> columnNames) {
+		return conn.getDatabase(dbName, columnNames.stream()
+				.map(Column::of)
+				.toList(), DatabaseOptionsBuilder.builder()
+				.openAsSecondary(true)
+				.absoluteConsistency(true)
+				.allowMemoryMapping(true)
+				.blockCache(Nullablelong.empty())
+				.lowMemory(false)
+				.maxOpenFiles(Nullableint.of(-1))
+				.optimistic(false)
+				.spinning(false)
+				.useDirectIO(false)
+				.extraFlags(Map.of())
+				.logPath(NullableString.empty())
+				.walPath(NullableString.empty())
+				.secondaryDirectoryName(NullableString.of("scan-all"))
+				.persistentCaches(List.of())
+				.volumes(Stream.of(
+						DatabaseVolume.of(Path.of(conn.getDatabasePath(dbName).toString()), -1),
+						DatabaseVolume.of(Path.of(conn.getDatabasePath(dbName).toString() + "_hot"), -1),
+						DatabaseVolume.of(Path.of(conn.getDatabasePath(dbName).toString() + "_cold"), -1),
+						DatabaseVolume.of(Path.of(conn.getDatabasePath(dbName).toString() + "_colder"), -1)
+				).filter(x -> Files.exists(x.volumePath())).toList())
+				.defaultColumnOptions(DefaultColumnOptions.of(
+						List.of(),
+						Nullablelong.empty(),
+						Nullableboolean.empty(),
+						Nullableboolean.empty(),
+						NullableFilter.empty(),
+						Nullableint.empty(),
+						NullableString.empty(),
+						Nullablelong.empty(),
+						false,
+						Nullablelong.empty(),
+						Nullablelong.empty(),
+						NullableCompression.empty()
+				))
+				.columnOptions(columnNames.stream()
+						.map(columnName -> NamedColumnOptions.of(columnName,
+								List.of(),
+								Nullablelong.empty(),
+								Nullableboolean.empty(),
+								Nullableboolean.empty(),
+								NullableFilter.empty(),
+								Nullableint.empty(),
+								NullableString.empty(),
+								Nullablelong.empty(),
+								false,
+								Nullablelong.empty(),
+								Nullablelong.empty(),
+								NullableCompression.empty()))
+						.toList())
+				.writeBufferManager(Nullablelong.empty())
+				.build());
+	}
+
+	private static void printHelp(List<String> args) {
+		System.err.println("""
+		Usage: repair scan-all DIRECTORY DB_NAME COLUMN_NAME...
+		   or: repair dump-all DIRECTORY DB_NAME COLUMN_NAME...
+		   or: repair verify-checksum DIRECTORY DB_NAME
+		   or: repair list-column-families DIRECTORY DB_NAME
+		""");
+		System.exit(1);
+	}
+}

src/repair/resources/log4j2.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration shutdownHook="disable" packages="org.yotsuba.logs">
+  <Appenders>
+
+    <Console name="Console">
+      <PatternLayout
+        pattern="%highlight{${LOG_LEVEL_PATTERN:-%p}}{FATAL=red blink, ERROR=red, WARN=yellow bold, INFO=green, DEBUG=green bold, TRACE=blue}: %m%n"/>
+    </Console>
+
+    <Async name="Async">
+      <AppenderRef ref="Console"/>
+    </Async>
+
+  </Appenders>
+  <Loggers>
+    <AsyncRoot level="INFO">
+      <filters>
+        <MarkerFilter marker="NETWORK_PACKETS" onMatch="DENY" onMismatch="NEUTRAL"/>
+      </filters>
+      <AppenderRef ref="Async"/>
+    </AsyncRoot>
+  </Loggers>
+</Configuration>

src/test/java/it/cavallium/dbengine/tests/LLRangeTest.java

@@ -0,0 +1,120 @@
+package it.cavallium.dbengine.tests;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import it.cavallium.buffer.Buf;
+import it.cavallium.dbengine.database.LLRange;
+import it.cavallium.dbengine.database.LLUtils;
+import it.cavallium.dbengine.database.disk.LLLocalDictionary;
+import java.math.BigInteger;
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Stream;
+import org.jetbrains.annotations.Nullable;
+import org.junit.jupiter.api.Assertions;
+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.ArgumentsSource;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class LLRangeTest {
+
+	private void printRanges(LLRange range, List<LLRange> ranges) {
+		for (int i = 1, size = ranges.size(); i < size; i++) {
+			LLRange prev = ranges.get(i - 1);
+			LLRange cur = ranges.get(i);
+			assertEquals(0, Objects.compare(prev.getMax(), cur.getMin(), Comparator.nullsFirst(Comparator.naturalOrder())));
+		}
+		System.out.println(toStringRange(range) + " ---> " + String.join(", ", ranges.stream().map(this::toStringRange).toList()));
+	}
+
+	private String toStringRange(LLRange r) {
+		if (r.isSingle()) {
+			return LLUtils.HEX_FORMAT.formatHex(r.getSingle().toByteArray());
+		} else if (r.hasMin() && r.hasMax()) {
+			return LLUtils.HEX_FORMAT.formatHex(r.getMin().toByteArray())
+					+ "-"
+					+ LLUtils.HEX_FORMAT.formatHex(r.getMax().toByteArray());
+		} else if (r.hasMin()) {
+			return LLUtils.HEX_FORMAT.formatHex(r.getMin().toByteArray()) + "-MAX";
+		} else if (r.hasMax()) {
+			return "MIN-" + LLUtils.HEX_FORMAT.formatHex(r.getMax().toByteArray());
+		} else {
+			return "MIN-MAX";
+		}
+	}
+
+	@Test
+	void parallelizeRange() {
+		var minBi = BigInteger.valueOf(50);
+		var maxBi = BigInteger.valueOf(100);
+		var range = LLRange.of(Buf.wrap(minBi.toByteArray()), Buf.wrap(maxBi.toByteArray()));
+		var ranges = LLLocalDictionary.parallelizeRange(range, 8).toList();
+		printRanges(range, ranges);
+	}
+
+	@Test
+	void parallelizeRangeNegative() {
+		var minBi = BigInteger.valueOf(Byte.MIN_VALUE);
+		var maxBi = BigInteger.valueOf(-50);
+		var range = LLRange.of(Buf.wrap(minBi.toByteArray()), Buf.wrap(maxBi.toByteArray()));
+		var ranges = LLLocalDictionary.parallelizeRange(range, 8).toList();
+		printRanges(range, ranges);
+	}
+
+	@Test
+	void parallelizeRangeNegativeToPositive() {
+		var minBi = BigInteger.valueOf(0);
+		var maxBi = BigInteger.valueOf(Byte.MIN_VALUE);
+		var range = LLRange.of(Buf.wrap(minBi.toByteArray()), Buf.wrap(maxBi.toByteArray()));
+		var ranges = LLLocalDictionary.parallelizeRange(range, 8).toList();
+		printRanges(range, ranges);
+	}
+
+	@Test
+	void parallelizeRangeMin() {
+		var minBi = BigInteger.valueOf(50);
+		var range = LLRange.of(Buf.wrap(minBi.toByteArray()), null);
+		var ranges = LLLocalDictionary.parallelizeRange(range, 8).toList();
+		printRanges(range, ranges);
+	}
+
+	@Test
+	void parallelizeRangeMax() {
+		var maxBi = BigInteger.valueOf(50);
+		var range = LLRange.of(null, Buf.wrap(maxBi.toByteArray()));
+		var ranges = LLLocalDictionary.parallelizeRange(range, 8).toList();
+		printRanges(range, ranges);
+	}
+
+	@ParameterizedTest
+	@MethodSource("provideRanges")
+	public void intersectTest(IntersectArgs args) {
+		Assertions.assertEquals(args.expected, LLRange.intersect(args.rangeA, args.rangeB));
+	}
+
+	public record IntersectArgs(LLRange expected, LLRange rangeA, LLRange rangeB) {}
+
+	public static Stream<IntersectArgs> provideRanges() {
+		return Stream.of(
+				new IntersectArgs(LLRange.all(), LLRange.all(), LLRange.all()),
+				new IntersectArgs(LLRange.single(Buf.wrap((byte) 1)), LLRange.single(Buf.wrap((byte) 1)), LLRange.all()),
+				new IntersectArgs(LLRange.single(Buf.wrap((byte) 1)), LLRange.all(), LLRange.single(Buf.wrap((byte) 1))),
+				new IntersectArgs(null, LLRange.single(Buf.wrap((byte) 1)), LLRange.single(Buf.wrap((byte) 2))),
+				new IntersectArgs(null, LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 2), Buf.wrap((byte) 3))),
+				new IntersectArgs(LLRange.single(Buf.wrap((byte) 1)), LLRange.single(Buf.wrap((byte) 1)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2))),
+				new IntersectArgs(LLRange.single(Buf.wrap((byte) 1)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.single(Buf.wrap((byte) 1))),
+				new IntersectArgs(null, LLRange.single(Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2))),
+				new IntersectArgs(null, LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.single(Buf.wrap((byte) 2))),
+				new IntersectArgs(null, LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 3), Buf.wrap((byte) 4))),
+				new IntersectArgs(null, LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 2), Buf.wrap((byte) 3))),
+				new IntersectArgs(LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 3))),
+				new IntersectArgs(LLRange.of(Buf.wrap((byte) 4), Buf.wrap((byte) 7)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 7)), LLRange.of(Buf.wrap((byte) 4), Buf.wrap((byte) 9))),
+				new IntersectArgs(LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2))),
+				new IntersectArgs(null, LLRange.of(Buf.wrap((byte) 1), Buf.wrap((byte) 2)), LLRange.of(Buf.wrap((byte) 3), Buf.wrap((byte) 4)))
+		);
+	}
+}

src/test/java/module-info.java

@@ -14,4 +14,5 @@ module dbengine.tests {
 	requires org.apache.commons.lang3;
 	requires rocksdbjni;
 	opens it.cavallium.dbengine.tests;
+	opens it.cavallium.dbengine.database.disk.test;
 }