adressing comments and simplifying code

Author: normen662

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/AbstractNode.java

@@ -45,10 +45,6 @@ abstract class AbstractNode<N extends NodeReference> implements Node<N> {
 
     /**
      * Constructs a new {@code AbstractNode} with a specified primary key and a list of neighbors.
-     * <p>
-     * This constructor creates a defensive, immutable copy of the provided {@code neighbors} list.
-     * This ensures that the internal state of the node cannot be modified by external
-     * changes to the original list after construction.
      *
      * @param primaryKey the unique identifier for this node; must not be {@code null}
      * @param neighbors the list of nodes connected to this node; must not be {@code null}

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/AbstractStorageAdapter.java

@@ -36,7 +36,7 @@
 /**
  * An abstract base class for {@link StorageAdapter} implementations.
  * <p>
- * This class provides the common infrastructure for managing HNSW graph data within {@link Subspace}.
+ * This class provides the common infrastructure for managing HNSW graph data within a {@link Subspace}.
  * It handles the configuration, node creation, and listener management, while delegating the actual
  * storage-specific read and write operations to concrete subclasses through the {@code fetchNodeInternal}
  * and {@code writeNodeInternal} abstract methods.

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/AggregatedVector.java

@@ -21,9 +21,14 @@
 package com.apple.foundationdb.async.hnsw;
 
 import com.apple.foundationdb.linear.RealVector;
+import com.google.common.base.Objects;
 
 import javax.annotation.Nonnull;
 
+/**
+ * A record-like class wrapping a {@link RealVector} and a count. This data structure is used to keep a running sum
+ * of many vectors in order to compute their centroid at a later time.
+ */
 class AggregatedVector {
     private final int partialCount;
     @Nonnull
@@ -44,20 +49,17 @@ public RealVector getPartialVector() {
     }
 
     @Override
-    public final boolean equals(final Object o) {
+    public boolean equals(final Object o) {
         if (!(o instanceof AggregatedVector)) {
             return false;
         }
-
         final AggregatedVector that = (AggregatedVector)o;
-        return partialCount == that.partialCount && partialVector.equals(that.partialVector);
+        return partialCount == that.partialCount && Objects.equal(partialVector, that.partialVector);
     }
 
     @Override
     public int hashCode() {
-        int result = partialCount;
-        result = 31 * result + partialVector.hashCode();
-        return result;
+        return Objects.hashCode(partialCount, partialVector);
     }
 
     @Override

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/CompactStorageAdapter.java

@@ -57,9 +57,6 @@ class CompactStorageAdapter extends AbstractStorageAdapter<NodeReference> implem
 
     /**
      * Constructs a new {@code CompactStorageAdapter}.
-     * <p>
-     * This constructor initializes the adapter by delegating to the superclass,
-     * setting up the necessary components for managing an HNSW graph.
      *
      * @param config the HNSW graph configuration, must not be null. See {@link Config}.
      * @param nodeFactory the factory used to create new nodes of type {@link NodeReference}, must not be null.

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/EntryNodeReference.java

@@ -77,9 +77,6 @@ public EntryNodeReference withVector(@Nonnull RealVector newVector) {
      */
     @Override
     public boolean equals(final Object o) {
-        if (!(o instanceof EntryNodeReference)) {
-            return false;
-        }
         if (!super.equals(o)) {
             return false;
         }

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/HNSW.java

@@ -1547,34 +1547,4 @@ private boolean shouldMaintainStats(final int batchSize) {
         double pBatch = -Math.expm1(batchSize * Math.log1p(-getConfig().getMaintainStatsProbability()));
         return random.nextDouble() < pBatch;
     }
-
-    private static class NodeReferenceWithLayer extends NodeReferenceWithVector {
-        private final int layer;
-
-        public NodeReferenceWithLayer(@Nonnull final Tuple primaryKey, @Nonnull final RealVector vector,
-                                      final int layer) {
-            super(primaryKey, vector);
-            this.layer = layer;
-        }
-
-        public int getLayer() {
-            return layer;
-        }
-
-        @Override
-        public boolean equals(final Object o) {
-            if (!(o instanceof NodeReferenceWithLayer)) {
-                return false;
-            }
-            if (!super.equals(o)) {
-                return false;
-            }
-            return layer == ((NodeReferenceWithLayer)o).layer;
-        }
-
-        @Override
-        public int hashCode() {
-            return Objects.hash(super.hashCode(), layer);
-        }
-    }
 }

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/NodeReference.java

@@ -78,7 +78,10 @@ public NodeReferenceWithVector asNodeReferenceWithVector() {
      */
     @Override
     public boolean equals(final Object o) {
-        if (!(o instanceof NodeReference)) {
+        if (this == o) {
+            return true;
+        }
+        if (o.getClass() != this.getClass()) {
             return false;
         }
         final NodeReference that = (NodeReference)o;

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/NodeReferenceWithDistance.java

@@ -72,9 +72,6 @@ public double getDistance() {
      */
     @Override
     public boolean equals(final Object o) {
-        if (!(o instanceof NodeReferenceWithDistance)) {
-            return false;
-        }
         if (!super.equals(o)) {
             return false;
         }

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/NodeReferenceWithVector.java

@@ -94,9 +94,6 @@ public NodeReferenceWithVector asNodeReferenceWithVector() {
      */
     @Override
     public boolean equals(final Object o) {
-        if (!(o instanceof NodeReferenceWithVector)) {
-            return false;
-        }
         if (!super.equals(o)) {
             return false;
         }

fdb-extensions/src/main/java/com/apple/foundationdb/async/hnsw/StorageTransform.java

@@ -27,7 +27,12 @@
 
 import javax.annotation.Nonnull;
 
-public class StorageTransform extends AffineOperator {
+/**
+ * A special affine operator that uses a random rotator seeded by the current {@link AccessInfo} and a given
+ * (pre-rotated) centroid. This operator is used inside the HNSW to transform back and forth between the coordinate
+ * system of the client and the coordinate system that is currently employed in the HNSW.
+ */
+class StorageTransform extends AffineOperator {
     public StorageTransform(final long seed, final int numDimensions, @Nonnull final RealVector translationVector) {
         super(new FhtKacRotator(seed, numDimensions, 10), translationVector);
     }