kaivalnp commented on code in PR #14178: URL: https://github.com/apache/lucene/pull/14178#discussion_r1935086492
########## lucene/sandbox/src/java22/org/apache/lucene/sandbox/codecs/faiss/FaissKnnVectorsFormat.java: ########## @@ -0,0 +1,75 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.lucene.sandbox.codecs.faiss; + +import java.io.IOException; +import java.util.Locale; +import org.apache.lucene.codecs.KnnVectorsFormat; +import org.apache.lucene.codecs.KnnVectorsReader; +import org.apache.lucene.codecs.KnnVectorsWriter; +import org.apache.lucene.codecs.hnsw.FlatVectorScorerUtil; +import org.apache.lucene.codecs.lucene99.Lucene99FlatVectorsFormat; +import org.apache.lucene.index.SegmentReadState; +import org.apache.lucene.index.SegmentWriteState; + +public final class FaissKnnVectorsFormat extends KnnVectorsFormat { + public static final String NAME = FaissKnnVectorsFormat.class.getSimpleName(); + static final int VERSION_START = 0; + static final int VERSION_CURRENT = VERSION_START; + static final String META_CODEC_NAME = NAME + "Meta"; + static final String DATA_CODEC_NAME = NAME + "Data"; + static final String META_EXTENSION = "faissm"; + static final String DATA_EXTENSION = "faissd"; + + private final String description; + private final String indexParams; + private final KnnVectorsFormat rawVectorsFormat; + + public FaissKnnVectorsFormat() { + this("HNSW32", "efConstruction=200"); + } + + public FaissKnnVectorsFormat(String description, String indexParams) { + super(NAME); + this.description = description; + this.indexParams = indexParams; + this.rawVectorsFormat = + new Lucene99FlatVectorsFormat(FlatVectorScorerUtil.getLucene99FlatVectorsScorer()); Review Comment: Not all Faiss indexes store the original vectors (eg PQ) -- and trying to "reconstruct" vectors [may be lossy](https://github.com/facebookresearch/faiss/blob/9e03ef0bda4320d05d03570deb0ab14feec1054d/faiss/Index.h#L188).. This primarily affects merges, where vectors in smaller segments are read back to create a fresh one -- so we'd keep losing information with each merge In the ideal scenario we could use Faiss if the index stores full vectors (eg HNSWFlat), and only add raw vectors to Lucene for other indexes. For now I wasn't 100% sure on how to determine this, so I'm storing them in Lucene in all cases Note that these would only be loaded into memory during indexing, and not search (they aren't accessed by Faiss) Another point to note is that reading back vectors from Faiss has its own cost (latency if we read them [one-by-one](https://github.com/facebookresearch/faiss/blob/9e03ef0bda4320d05d03570deb0ab14feec1054d/faiss/Index.h#L194), or memory in case of a [bulk read](https://github.com/facebookresearch/faiss/blob/9e03ef0bda4320d05d03570deb0ab14feec1054d/faiss/Index.h#L214) and we may need some sort of batching) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
