diff --git a/java/server/src/main/java/org/softwareheritage/graph/Graph.java b/java/server/src/main/java/org/softwareheritage/graph/Graph.java
index 65dbeea..183b1e4 100644
--- a/java/server/src/main/java/org/softwareheritage/graph/Graph.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/Graph.java
@@ -1,212 +1,217 @@
 package org.softwareheritage.graph;
 
 import java.io.IOException;
 
 import it.unimi.dsi.big.webgraph.BVGraph;
 import it.unimi.dsi.lang.FlyweightPrototype;
 import it.unimi.dsi.big.webgraph.LazyLongIterator;
 
 import org.softwareheritage.graph.Node;
 import org.softwareheritage.graph.SwhPID;
 import org.softwareheritage.graph.backend.NodeIdMap;
 import org.softwareheritage.graph.backend.NodeTypesMap;
 
 /**
  * Main class storing the compressed graph and node id mappings.
  * <p>
  * The compressed graph is stored using the <a href="http://webgraph.di.unimi.it/">WebGraph</a>
  * ecosystem. Additional mappings are necessary because Software Heritage uses string based <a
  * href="https://docs.softwareheritage.org/devel/swh-model/persistent-identifiers.html">persistent
  * identifiers</a> (PID) while WebGraph uses integers internally. These two mappings (long id &harr;
  * PID) are used for the input (users refer to the graph using PID) and the output (convert back to
  * PID for users results). However, since graph traversal can be restricted depending on the node
  * type (see {@link AllowedEdges}), a long id &rarr; node type map is stored as well to avoid a full
  * PID lookup.
  *
  * @author The Software Heritage developers
  * @see org.softwareheritage.graph.AllowedEdges
  * @see org.softwareheritage.graph.backend.NodeIdMap
  * @see org.softwareheritage.graph.backend.NodeTypesMap
  */
 
 public class Graph implements FlyweightPrototype<Graph> {
     /** File extension for the SWH PID to long node id map */
     public static final String PID_TO_NODE = ".pid2node.csv";
     /** File extension for the long node id to SWH PID map */
     public static final String NODE_TO_PID = ".node2pid.csv";
     /** File extension for the long node id to node typ map */
     public static final String NODE_TO_TYPE = ".node2type.map";
 
     /** Compressed graph stored as a {@link it.unimi.dsi.big.webgraph.BVGraph} */
     BVGraph graph;
     /** Transposed compressed graph (used for backward traversals) */
     BVGraph graphTransposed;
     /** Path and basename of the compressed graph */
     String path;
     /** Mapping long id &harr; SWH PIDs */
     NodeIdMap nodeIdMap;
     /** Mapping long id &rarr; node types */
     NodeTypesMap nodeTypesMap;
 
     /**
      * Constructor.
      *
      * @param path path and basename of the compressed graph to load
      */
     public Graph(String path) throws IOException {
         this.graph = BVGraph.load(path);
         this.graphTransposed = BVGraph.load(path + "-transposed");
         this.path = path;
-        this.nodeIdMap = new NodeIdMap(path, getNbNodes());
         this.nodeTypesMap = new NodeTypesMap(path);
+
+        // TODO: we don't need to load the nodeIdMap now that all the
+        // translation between ints and PIDs is happening on the Python side.
+        // However, some parts of the code still depend on this, so it's
+        // commented out while we decide on what to do with it.
+        this.nodeIdMap = null; // new NodeIdMap(path, getNbNodes());
     }
 
     // Protected empty constructor to implement copy()
     protected Graph() { }
 
     /**
      * Return a flyweight copy of the graph.
      */
     @Override
     public Graph copy() {
         final Graph ng = new Graph();
         ng.graph = this.graph.copy();
         ng.graphTransposed = this.graphTransposed.copy();
         ng.path = path;
         ng.nodeIdMap = this.nodeIdMap;
         ng.nodeTypesMap = this.nodeTypesMap;
         return ng;
     }
 
     /**
      * Cleans up graph resources after use.
      */
     public void cleanUp() throws IOException {
         nodeIdMap.close();
     }
 
     /**
      * Returns the graph full path.
      *
      * @return graph full path
      */
     public String getPath() {
         return path;
     }
 
     /**
      * Converts {@link SwhPID} node to long.
      *
      * @param swhPID node specified as a {@link SwhPID}
      * @return internal long node id
      * @see org.softwareheritage.graph.SwhPID
      */
     public long getNodeId(SwhPID swhPID) {
         return nodeIdMap.getNodeId(swhPID);
     }
 
     /**
      * Converts long id node to {@link SwhPID}.
      *
      * @param nodeId node specified as a long id
      * @return external SWH PID
      * @see org.softwareheritage.graph.SwhPID
      */
     public SwhPID getSwhPID(long nodeId) {
         return nodeIdMap.getSwhPID(nodeId);
     }
 
     /**
      * Returns node type.
      *
      * @param nodeId node specified as a long id
      * @return corresponding node type
      * @see org.softwareheritage.graph.Node.Type
      */
     public Node.Type getNodeType(long nodeId) {
         return nodeTypesMap.getType(nodeId);
     }
 
     /**
      * Returns number of nodes in the graph.
      *
      * @return number of nodes in the graph
      */
     public long getNbNodes() {
         return graph.numNodes();
     }
 
     /**
      * Returns number of edges in the graph.
      *
      * @return number of edges in the graph
      */
     public long getNbEdges() {
         return graph.numArcs();
     }
 
     /**
      * Returns lazy iterator of successors of a node.
      *
      * @param nodeId node specified as a long id
      * @return lazy iterator of successors of the node, specified as a <a
      * href="http://webgraph.di.unimi.it/">WebGraph</a> LazyLongIterator
      */
     public LazyLongIterator successors(long nodeId) {
         return graph.successors(nodeId);
     }
 
     /**
      * Returns the outdegree of a node.
      *
      * @param nodeId node specified as a long id
      * @return outdegree of a node
      */
     public long outdegree(long nodeId) {
         return graph.outdegree(nodeId);
     }
 
     /**
      * Returns lazy iterator of predecessors of a node.
      *
      * @param nodeId node specified as a long id
      * @return lazy iterator of predecessors of the node, specified as a <a
      * href="http://webgraph.di.unimi.it/">WebGraph</a> LazyLongIterator
      */
     public LazyLongIterator predecessors(long nodeId) {
         return graphTransposed.successors(nodeId);
     }
 
     /**
      * Returns the indegree of a node.
      *
      * @param nodeId node specified as a long id
      * @return indegree of a node
      */
     public long indegree(long nodeId) {
         return graphTransposed.outdegree(nodeId);
     }
 
     /**
      * Returns the degree of a node, depending on graph orientation.
      *
      * @param nodeId node specified as a long id
      * @param useTransposed boolean value to use transposed graph
      * @return degree of a node
      */
     public long degree(long nodeId, boolean useTransposed) {
         return (useTransposed) ? indegree(nodeId) : outdegree(nodeId);
     }
 
     /**
      * Returns the neighbors of a node (as a lazy iterator), depending on graph orientation.
      *
      * @param nodeId node specified as a long id
      * @param useTransposed boolean value to use transposed graph
      * @return lazy iterator of neighbors of the node, specified as a <a
      * href="http://webgraph.di.unimi.it/">WebGraph</a> LazyLongIterator
      */
     public LazyLongIterator neighbors(long nodeId, boolean useTransposed) {
         return (useTransposed) ? predecessors(nodeId) : successors(nodeId);
     }
 }