Add a basic generic HNSW implementation

Author: thecoop

server/src/main/java/org/elasticsearch/index/codec/vectors/es93/ES93HnswVectorsFormat.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.index.codec.vectors.es93;
+
+import org.apache.lucene.codecs.KnnVectorsReader;
+import org.apache.lucene.codecs.KnnVectorsWriter;
+import org.apache.lucene.codecs.hnsw.FlatVectorsFormat;
+import org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsReader;
+import org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsWriter;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+import org.elasticsearch.index.codec.vectors.AbstractHnswVectorsFormat;
+
+import java.io.IOException;
+
+public class ES93HnswVectorsFormat extends AbstractHnswVectorsFormat {
+
+    static final String NAME = "ES93HnswVectorsFormat";
+
+    private final FlatVectorsFormat flatVectorsFormat;
+
+    public ES93HnswVectorsFormat() {
+        super(NAME);
+        flatVectorsFormat = new ES93GenericFlatVectorsFormat();
+    }
+
+    public ES93HnswVectorsFormat(int maxConn, int beamWidth, boolean bfloat16, boolean useDirectIO) {
+        super(NAME, maxConn, beamWidth);
+        flatVectorsFormat = new ES93GenericFlatVectorsFormat(bfloat16, useDirectIO);
+    }
+
+    @Override
+    protected FlatVectorsFormat flatVectorsFormat() {
+        return flatVectorsFormat;
+    }
+
+    @Override
+    public KnnVectorsWriter fieldsWriter(SegmentWriteState state) throws IOException {
+        return new Lucene99HnswVectorsWriter(state, maxConn, beamWidth, flatVectorsFormat.fieldsWriter(state), numMergeWorkers, mergeExec);
+    }
+
+    @Override
+    public KnnVectorsReader fieldsReader(SegmentReadState state) throws IOException {
+        return new Lucene99HnswVectorsReader(state, flatVectorsFormat.fieldsReader(state));
+    }
+}