diff --git a/api/server/pom.xml b/api/server/pom.xml
index d68bb29..8e4f6d0 100644
--- a/api/server/pom.xml
+++ b/api/server/pom.xml
@@ -1,121 +1,127 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
     <groupId>org.softwareheritage.graph</groupId>
     <artifactId>graph</artifactId>
     <version>1.0-ALPHA</version>
 
     <name>graph</name>
     <url>https://www.softwareheritage.org/</url>
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
     </properties>
 
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.11</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>io.javalin</groupId>
             <artifactId>javalin</artifactId>
             <version>2.8.0</version>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
             <version>1.7.26</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
             <version>2.9.8</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>webgraph-big</artifactId>
             <version>3.5.0</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>fastutil</artifactId>
             <version>8.2.2</version>
         </dependency>
     </dependencies>
 
     <build>
         <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
             <plugins>
                 <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                 <plugin>
                     <artifactId>maven-clean-plugin</artifactId>
                     <version>3.1.0</version>
                 </plugin>
                 <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                 <plugin>
                     <artifactId>maven-resources-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-compiler-plugin</artifactId>
                     <version>3.8.0</version>
+                    <configuration>
+                        <compilerArgs>
+                            <arg>-verbose</arg>
+                            <arg>-Xlint:all</arg>
+                        </compilerArgs>
+                    </configuration>
                 </plugin>
                 <plugin>
                     <artifactId>maven-surefire-plugin</artifactId>
                     <version>2.22.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-jar-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-install-plugin</artifactId>
                     <version>2.5.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-deploy-plugin</artifactId>
                     <version>2.8.2</version>
                 </plugin>
                 <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                 <plugin>
                     <artifactId>maven-site-plugin</artifactId>
                     <version>3.7.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-project-info-reports-plugin</artifactId>
                     <version>3.0.0</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-assembly-plugin</artifactId>
                     <configuration>
                         <archive>
                             <manifest>
                                 <mainClass>org.softwareheritage.graph.App</mainClass>
                             </manifest>
                         </archive>
                         <descriptorRefs>
                             <descriptorRef>jar-with-dependencies</descriptorRef>
                         </descriptorRefs>
                     </configuration>
                     <executions>
                         <execution>
                             <id>make-assembly</id> <!-- this is used for inheritance merges -->
                             <phase>package</phase> <!-- bind to the packaging phase -->
                             <goals>
                                 <goal>single</goal>
                             </goals>
                         </execution>
                     </executions>
                 </plugin>
             </plugins>
         </pluginManagement>
     </build>
 </project>
diff --git a/api/server/src/main/java/org/softwareheritage/graph/Dataset.java b/api/server/src/main/java/org/softwareheritage/graph/Dataset.java
index 410c13c..cdf0e14 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/Dataset.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/Dataset.java
@@ -1,125 +1,126 @@
 package org.softwareheritage.graph;
 
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.zip.GZIPInputStream;
 
 import it.unimi.dsi.big.webgraph.BVGraph;
 import it.unimi.dsi.big.webgraph.LazyLongIterator;
 import it.unimi.dsi.fastutil.io.BinIO;
 import it.unimi.dsi.fastutil.longs.LongBigArrays;
 import it.unimi.dsi.fastutil.objects.Object2LongFunction;
 import it.unimi.dsi.io.FastBufferedReader;
 import it.unimi.dsi.io.LineIterator;
 import it.unimi.dsi.lang.MutableString;
 
 public class Dataset
 {
     public enum Name {
         DIR_TO_DIR,
         DIR_TO_FILE,
         DIR_TO_REV,
         ORIGIN_TO_SNAPSHOT,
         RELEASE_TO_OBJ,
         REV_TO_DIR,
         REV_TO_REV,
         SNAPSHOT_TO_OBJ
     }
 
     BVGraph graph;
     String path;
     HashMap<String, Long> hashToNode;
     HashMap<Long, String> nodeToHash;
 
     public Dataset(String datasetPath)
     {
         try {
             this.graph = BVGraph.load(datasetPath);
             this.path = datasetPath;
             setupNodesMapping();
         } catch (Exception e) {
             System.out.println("[WARNING] Could not load dataset " + datasetPath + ": " + e);
         }
     }
 
     void setupNodesMapping() throws IOException, ClassNotFoundException
     {
         this.hashToNode = new HashMap<String, Long>();
         this.nodeToHash = new HashMap<Long, String>();
 
         // First mapping: SWH hexhash (strings) <=> WebGraph MPH (longs)
         HashMap<Long, String> mphToHash = new HashMap<Long, String>();
+        @SuppressWarnings("unchecked")
         Object2LongFunction<String> mphMap =
             (Object2LongFunction<String>) BinIO.loadObject(path + ".mph");
 
         InputStream nodeFile = new FileInputStream(path + ".nodes.csv.gz");
         Collection<MutableString> hashes =
             new LineIterator(
             new FastBufferedReader(
             new InputStreamReader(
             new GZIPInputStream(nodeFile), "UTF-8"))).allLines();
 
         for (MutableString h : hashes)
         {
             String hash = new String(h.toString());
             long mph = mphMap.getLong(hash);
             mphToHash.put(mph, hash);
         }
 
         // Second mapping: WebGraph MPH (longs) <=> BFS ordering (longs)
         long n = mphMap.size();
         long[][] bfsMap = LongBigArrays.newBigArray(n);
         long loaded = BinIO.loadLongs(path + ".order", bfsMap);
         if (loaded != n)
             throw new IllegalArgumentException("Graph contains " + n + " nodes, but read " + loaded);
 
         // Create final mapping: SWH hexhash (strings) <=> BFS ordering (longs)
         for (long id = 0; id < n; id++)
         {
             String hash = mphToHash.get(id);
             long node = LongBigArrays.get(bfsMap, id);
 
             hashToNode.put(hash, node);
             nodeToHash.put(node, hash);
         }
     }
 
     public String getPath()
     {
         return path;
     }
 
     public long getNode(String hash)
     {
         return hashToNode.get(hash);
     }
 
     public String getHash(long node)
     {
         return nodeToHash.get(node);
     }
 
     public long getNbNodes()
     {
         return graph.numNodes();
     }
 
     public long getNbEdges()
     {
         return graph.numArcs();
     }
 
     public LazyLongIterator successors(long node)
     {
         return graph.successors(node);
     }
 
     public long outdegree(long node)
     {
         return graph.outdegree(node);
     }
 }