jpountz commented on code in PR #11860: URL: https://github.com/apache/lucene/pull/11860#discussion_r1025393090
########## lucene/core/src/java/org/apache/lucene/codecs/lucene95/Lucene95HnswVectorsFormat.java: ########## @@ -0,0 +1,168 @@ +/* + * 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.codecs.lucene95; + +import java.io.IOException; +import org.apache.lucene.codecs.KnnVectorsFormat; +import org.apache.lucene.codecs.KnnVectorsReader; +import org.apache.lucene.codecs.KnnVectorsWriter; +import org.apache.lucene.codecs.lucene90.IndexedDISI; +import org.apache.lucene.index.SegmentReadState; +import org.apache.lucene.index.SegmentWriteState; +import org.apache.lucene.search.DocIdSetIterator; +import org.apache.lucene.store.IndexOutput; +import org.apache.lucene.util.hnsw.HnswGraph; + +/** + * Lucene 9.4 vector format, which encodes numeric vector values and an optional associated graph + * connecting the documents having values. The graph is used to power HNSW search. The format + * consists of three files: + * + * <h2>.vec (vector data) file</h2> + * + * <p>For each field: + * + * <ul> + * <li>Vector data ordered by field, document ordinal, and vector dimension. When the + * vectorEncoding is BYTE, each sample is stored as a single byte. When it is FLOAT32, each + * sample is stored as an IEEE float in little-endian byte order. + * <li>DocIds encoded by {@link IndexedDISI#writeBitSet(DocIdSetIterator, IndexOutput, byte)}, + * note that only in sparse case + * <li>OrdToDoc was encoded by {@link org.apache.lucene.util.packed.DirectMonotonicWriter}, note + * that only in sparse case + * </ul> + * + * <h2>.vex (vector index)</h2> + * + * <p>Stores graphs connecting the documents for each field organized as a list of nodes' neighbours + * as following: + * + * <ul> + * <li>For each level: + * <ul> + * <li>For each node: + * <ul> + * <li><b>[int32]</b> the number of neighbor nodes + * <li><b>array[int32]</b> the neighbor ordinals + * <li><b>array[int32]</b> padding if the number of the node's neighbors is less than + * the maximum number of connections allowed on this level. Padding is equal to + * ((maxConnOnLevel – the number of neighbours) * 4) bytes. + * </ul> + * </ul> + * </ul> + * + * <h2>.vem (vector metadata) file</h2> + * + * <p>For each field: + * + * <ul> + * <li><b>[int32]</b> field number + * <li><b>[int32]</b> vector similarity function ordinal + * <li><b>[vlong]</b> offset to this field's vectors in the .vec file + * <li><b>[vlong]</b> length of this field's vectors, in bytes + * <li><b>[vlong]</b> offset to this field's index in the .vex file + * <li><b>[vlong]</b> length of this field's index data, in bytes + * <li><b>[int]</b> dimension of this field's vectors + * <li><b>[int]</b> the number of documents having values for this field + * <li><b>[int8]</b> if equals to -1, dense – all documents have values for a field. If equals to + * 0, sparse – some documents missing values. + * <li>DocIds were encoded by {@link IndexedDISI#writeBitSet(DocIdSetIterator, IndexOutput, byte)} + * <li>OrdToDoc was encoded by {@link org.apache.lucene.util.packed.DirectMonotonicWriter}, note + * that only in sparse case + * <li><b>[int]</b> the maximum number of connections (neigbours) that each node can have + * <li><b>[int]</b> number of levels in the graph + * <li>Graph nodes by level. For each level + * <ul> + * <li><b>[int]</b> the number of nodes on this level + * <li><b>array[int]</b> for levels greater than 0 list of nodes on this level, stored as + * the level 0th nodes' ordinals. + * </ul> + * </ul> + * + * @lucene.experimental + */ +public final class Lucene95HnswVectorsFormat extends KnnVectorsFormat { + + static final String META_CODEC_NAME = "lucene95HnswVectorsFormatMeta"; Review Comment: nit: we generally use titlecase for codec names ```suggestion static final String META_CODEC_NAME = "Lucene95HnswVectorsFormatMeta"; ``` -- 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. 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