mike-tr-adamson commented on code in PR #2409: URL: https://github.com/apache/cassandra/pull/2409#discussion_r1227912226
########## src/java/org/apache/cassandra/index/sai/disk/v1/kdtree/BKDWriter.java: ########## @@ -0,0 +1,782 @@ +/* + * 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.cassandra.index.sai.disk.v1.kdtree; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.List; +import java.util.function.IntFunction; + +import com.google.common.base.MoreObjects; + +import org.apache.cassandra.index.sai.disk.io.RAMIndexOutput; +import org.apache.cassandra.index.sai.disk.v1.SAICodecUtils; +import org.apache.lucene.codecs.MutablePointValues; +import org.apache.lucene.store.DataOutput; +import org.apache.lucene.store.GrowableByteArrayDataOutput; +import org.apache.lucene.store.IndexOutput; +import org.apache.lucene.util.ArrayUtil; +import org.apache.lucene.util.BytesRef; +import org.apache.lucene.util.FutureArrays; +import org.apache.lucene.util.IntroSorter; +import org.apache.lucene.util.LongBitSet; +import org.apache.lucene.util.Sorter; +import org.apache.lucene.util.bkd.MutablePointsReaderUtils; + +/** + * This is a specialisation of the lucene BKDWriter that only writes a single dimension. + * <p> + * Recursively builds a block KD-tree to assign all incoming points in N-dim space to smaller + * and smaller N-dim rectangles (cells) until the number of points in a given + * rectangle is <= <code>maxPointsInLeafNode</code>. The tree is + * fully balanced, which means the leaf nodes will have between 50% and 100% of + * the requested <code>maxPointsInLeafNode</code>. Values that fall exactly + * on a cell boundary may be in either cell. + * + * <p> + * See <a href="https://www.cs.duke.edu/~pankaj/publications/papers/bkd-sstd.pdf";>this paper</a> for details. + * + * <p>This consumes heap during writing: it allocates a <code>LongBitSet(numPoints)</code>, + * and then uses up to the specified {@code maxMBSortInHeap} heap space for writing. + * + * <p> + * <b>NOTE</b>: This can write at most Integer.MAX_VALUE * <code>maxPointsInLeafNode</code> total points. + * + * lucene.experimental + */ +public class BKDWriter Review Comment: I would prefer `BlockBalancedTree` as a general descriptive name for this structure, but `blockbalancedtree` is a bit of a mouthful for a package name, or is it? The alternative would be to leave the classes using `BlockBalancedTree` and use `bbtree` for the package. WDYT? -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
