maedhroz commented on code in PR #2409: URL: https://github.com/apache/cassandra/pull/2409#discussion_r1228799186
########## src/java/org/apache/cassandra/index/sai/disk/v1/bbtree/BlockBalancedTreeWriter.java: ########## @@ -0,0 +1,766 @@ +/* + * 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.bbtree; + +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.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.Sorter; +import org.apache.lucene.util.bkd.MutablePointsReaderUtils; + +/** + * This is a specialisation of the lucene BKDWriter that only writes a single dimension + * balanced tree. + * <p> + * Recursively builds a block balanced tree to assign all incoming points to smaller + * and smaller 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> + * <b>NOTE</b>: This can write at most Integer.MAX_VALUE * <code>maxPointsInLeafNode</code> total points. + */ +public class BlockBalancedTreeWriter +{ + // Enable to check that values are added to the tree in correct order and within bounds + private static final boolean DEBUG = false; + + // Default maximum number of point in each leaf block + public static final int DEFAULT_MAX_POINTS_IN_LEAF_NODE = 1024; + + private final int bytesPerValue; + private final BytesRef scratchBytesRef1 = new BytesRef(); + private final int maxPointsInLeafNode; + private final byte[] minPackedValue; + private final byte[] maxPackedValue; + private long pointCount; + private final long maxDoc; + + public BlockBalancedTreeWriter(long maxDoc, int bytesPerValue, int maxPointsInLeafNode) + { + if (maxPointsInLeafNode <= 0) + throw new IllegalArgumentException("maxPointsInLeafNode must be > 0; got " + maxPointsInLeafNode); + if (maxPointsInLeafNode > ArrayUtil.MAX_ARRAY_LENGTH) + throw new IllegalArgumentException("maxPointsInLeafNode must be <= ArrayUtil.MAX_ARRAY_LENGTH (= " + + ArrayUtil.MAX_ARRAY_LENGTH + "); got " + maxPointsInLeafNode); + + this.maxPointsInLeafNode = maxPointsInLeafNode; + this.bytesPerValue = bytesPerValue; + this.maxDoc = maxDoc; + + minPackedValue = new byte[bytesPerValue]; + maxPackedValue = new byte[bytesPerValue]; + } + + public long getPointCount() + { + return pointCount; + } + + public int getBytesPerValue() + { + return bytesPerValue; + } + + public int getMaxPointsInLeafNode() + { + return maxPointsInLeafNode; + } + + /** + * Write the point values from a {@link IntersectingPointValues}. The points can be reordered before writing + * to disk and does not use transient disk for reordering. + */ + public long writeField(IndexOutput out, IntersectingPointValues reader, + final Callback callback) throws IOException + { + SAICodecUtils.writeHeader(out); + + // We are only ever dealing with one dimension, so we can sort the points in ascending order + // and write out the values + if (reader.needsSorting()) + MutablePointsReaderUtils.sort(Math.toIntExact(maxDoc), bytesPerValue, reader, 0, Math.toIntExact(reader.size())); + + OneDimensionBKDWriter oneDimWriter = new OneDimensionBKDWriter(out, callback); + + reader.intersect((docID, packedValue) -> oneDimWriter.add(packedValue, docID)); + + long filePointer = oneDimWriter.finish(); + + SAICodecUtils.writeFooter(out); + return filePointer; + } + + interface Callback + { + void writeLeafDocs(RowIDAndIndex[] leafDocs, int offset, int count); + } + + public static class RowIDAndIndex Review Comment: ```suggestion static class RowIDAndIndex ``` -- This is an automated message from the Apache Git Service. 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