Adjust backports for #14157 & #14174

Author: benwtrent

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene90/Lucene90HnswVectorsReader.java

@@ -488,6 +488,11 @@ public int entryNode() {
       throw new UnsupportedOperationException();
     }
 
+    @Override
+    public int maxConn() {
+      throw new UnsupportedOperationException();
+    }
+
     @Override
     public NodesIterator getNodesOnLevel(int level) {
       throw new UnsupportedOperationException();

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene90/Lucene90OnHeapHnswGraph.java

@@ -198,6 +198,11 @@ public int entryNode() {
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  public int maxConn() {
+    return maxConn;
+  }
+
   @Override
   public NodesIterator getNodesOnLevel(int level) {
     throw new UnsupportedOperationException();

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/Lucene91HnswVectorsReader.java

@@ -548,6 +548,11 @@ public int entryNode() {
       return entryNode;
     }
 
+    @Override
+    public int maxConn() {
+      return (int) bytesForConns / Integer.BYTES - 1;
+    }
+
     @Override
     public NodesIterator getNodesOnLevel(int level) {
       if (level == 0) {

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/Lucene91OnHeapHnswGraph.java

@@ -160,6 +160,11 @@ public int entryNode() {
     return entryNode;
   }
 
+  @Override
+  public int maxConn() {
+    return maxConn;
+  }
+
   @Override
   public NodesIterator getNodesOnLevel(int level) {
     if (level == 0) {

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene92/Lucene92HnswVectorsReader.java

@@ -459,6 +459,11 @@ public int entryNode() {
       return entryNode;
     }
 
+    @Override
+    public int maxConn() {
+      return (int) bytesForConns / Integer.BYTES - 1;
+    }
+
     @Override
     public NodesIterator getNodesOnLevel(int level) {
       if (level == 0) {

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene94/Lucene94HnswVectorsReader.java

@@ -448,6 +448,7 @@ private static final class OffHeapHnswGraph extends HnswGraph {
     final int size;
     final long bytesForConns;
     final long bytesForConns0;
+    final int maxConn;
 
     int arcCount;
     int arcUpTo;
@@ -463,6 +464,7 @@ private static final class OffHeapHnswGraph extends HnswGraph {
       this.bytesForConns = Math.multiplyExact(Math.addExact(entry.M, 1L), Integer.BYTES);
       this.bytesForConns0 =
           Math.multiplyExact(Math.addExact(Math.multiplyExact(entry.M, 2L), 1), Integer.BYTES);
+      maxConn = entry.M;
     }
 
     @Override
@@ -501,6 +503,11 @@ public int numLevels() {
       return numLevels;
     }
 
+    @Override
+    public int maxConn() {
+      return maxConn;
+    }
+
     @Override
     public int entryNode() {
       return entryNode;

Diff for: lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene95/Lucene95HnswVectorsReader.java

@@ -537,6 +537,11 @@ public int entryNode() throws IOException {
       return entryNode;
     }
 
+    @Override
+    public int maxConn() {
+      return currentNeighborsBuffer.length / 2;
+    }
+
     @Override
     public NodesIterator getNodesOnLevel(int level) {
       if (level == 0) {

Diff for: lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene94/Lucene94HnswVectorsWriter.java

@@ -334,6 +334,11 @@ public int numLevels() {
         return graph.numLevels();
       }
 
+      @Override
+      public int maxConn() {
+        return graph.maxConn();
+      }
+
       @Override
       public int entryNode() {
         throw new UnsupportedOperationException("Not supported on a mock graph");

Diff for: lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene95/Lucene95HnswVectorsWriter.java

@@ -366,6 +366,11 @@ public int entryNode() {
         throw new UnsupportedOperationException("Not supported on a mock graph");
       }
 
+      @Override
+      public int maxConn() {
+        throw new UnsupportedOperationException("Not supported on a mock graph");
+      }
+
       @Override
       public NodesIterator getNodesOnLevel(int level) {
         if (level == 0) {

Diff for: lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java

@@ -526,6 +526,11 @@ public int numLevels() throws IOException {
       return numLevels;
     }
 
+    @Override
+    public int maxConn() {
+      return currentNeighborsBuffer.length >> 1;
+    }
+
     @Override
     public int entryNode() throws IOException {
       return entryNode;

Diff for: lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsWriter.java

@@ -294,6 +294,11 @@ public int numLevels() {
         return graph.numLevels();
       }
 
+      @Override
+      public int maxConn() {
+        return graph.maxConn();
+      }
+
       @Override
       public int entryNode() {
         throw new UnsupportedOperationException("Not supported on a mock graph");

Diff for: lucene/core/src/java/org/apache/lucene/util/hnsw/HnswGraph.java

@@ -84,6 +84,9 @@ public int maxNodeId() {
   /** Returns the number of levels of the graph */
   public abstract int numLevels() throws IOException;
 
+  /** returns M, the maximum number of connections for a node. */
+  public abstract int maxConn() throws IOException;
+
   /** Returns graph's entry point on the top level * */
   public abstract int entryNode() throws IOException;
 
@@ -118,6 +121,11 @@ public int numLevels() {
           return 0;
         }
 
+        @Override
+        public int maxConn() {
+          return 0;
+        }
+
         @Override
         public int entryNode() {
           return 0;

Diff for: lucene/core/src/java/org/apache/lucene/util/hnsw/OnHeapHnswGraph.java

@@ -192,6 +192,11 @@ public int entryNode() {
     return entryNode.get().node;
   }
 
+  @Override
+  public int maxConn() {
+    return nsize - 1;
+  }
+
   /**
    * Try to set the entry node if the graph does not have one
    *

Diff for: lucene/core/src/test/org/apache/lucene/util/hnsw/HnswGraphTestCase.java

@@ -1337,6 +1337,11 @@ public int entryNode() throws IOException {
       return delegate.entryNode();
     }
 
+    @Override
+    public int maxConn() throws IOException {
+      return delegate.maxConn();
+    }
+
     @Override
     public NodesIterator getNodesOnLevel(int level) throws IOException {
       return delegate.getNodesOnLevel(level);

Diff for: lucene/core/src/test/org/apache/lucene/util/hnsw/TestHnswUtil.java

@@ -250,6 +250,11 @@ public int entryNode() {
       return 0;
     }
 
+    @Override
+    public int maxConn() {
+      return 0;
+    }
+
     @Override
     public String toString() {
       StringBuilder buf = new StringBuilder();