addressing more comments

Author: normen662

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

@@ -21,6 +21,7 @@
 package com.apple.foundationdb.async.hnsw;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.concurrent.CompletableFuture;
 
 /**
@@ -67,12 +68,12 @@ default void onNodeRead(int layer, @Nonnull Node<? extends NodeReference> node)
      * The default implementation is a no-op and does nothing.
      * @param layer the layer from which the key-value pair was read.
      * @param key the key that was read, guaranteed to be non-null.
-     * @param value the value associated with the key, guaranteed to be non-null.
+     * @param value the value associated with the key, can be null if the key was not found
      */
     @SuppressWarnings("unused")
     default void onKeyValueRead(int layer,
                                 @Nonnull byte[] key,
-                                @Nonnull byte[] value) {
+                                @Nullable byte[] value) {
         // nothing
     }
 }

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

@@ -235,7 +235,7 @@ static RealVector vectorFromBytes(@Nonnull final Config config, @Nonnull final b
      */
     @Nonnull
     @SuppressWarnings("PrimitiveArrayArgumentToVarargsMethod")
-    static Tuple tupleFromVector(final RealVector vector) {
+    static Tuple tupleFromVector(@Nonnull final RealVector vector) {
         return Tuple.from(vector.getRawData());
     }
 
@@ -254,10 +254,10 @@ static CompletableFuture<AccessInfo> fetchAccessInfo(@Nonnull final Config confi
 
         return readTransaction.get(key)
                 .thenApply(valueBytes -> {
+                    onReadListener.onKeyValueRead(-1, key, valueBytes);
                     if (valueBytes == null) {
                         return null; // not a single node in the index
                     }
-                    onReadListener.onKeyValueRead(-1, key, valueBytes);
 
                     final Tuple entryTuple = Tuple.fromBytes(valueBytes);
                     final int layer = (int)entryTuple.getLong(0);
@@ -326,6 +326,7 @@ static CompletableFuture<List<AggregatedVector>> consumeSampledVectors(@Nonnull
                         final byte[] key = keyValue.getKey();
                         final byte[] value = keyValue.getValue();
                         resultBuilder.add(aggregatedVectorFromRaw(prefixSubspace, key, value));
+                        transaction.addReadConflictKey(key);
                         transaction.clear(key);
                         onReadListener.onKeyValueRead(-1, key, value);
                     }

fdb-extensions/src/test/java/com/apple/foundationdb/async/hnsw/HNSWTest.java

@@ -59,6 +59,7 @@
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.IOException;
 import java.nio.channels.FileChannel;
 import java.nio.file.Path;
@@ -495,9 +496,9 @@ public void onNodeRead(final int layer, @Nonnull final Node<? extends NodeRefere
         }
 
         @Override
-        public void onKeyValueRead(final int layer, @Nonnull final byte[] key, @Nonnull final byte[] value) {
+        public void onKeyValueRead(final int layer, @Nonnull final byte[] key, @Nullable final byte[] value) {
             bytesReadByLayer.compute(layer, (l, oldValue) -> (oldValue == null ? 0 : oldValue) +
-                    key.length + value.length);
+                    key.length + (value == null ? 0 : value.length));
         }
     }