yabola commented on code in PR #1042: URL: https://github.com/apache/parquet-mr/pull/1042#discussion_r1188564979
########## parquet-column/src/main/java/org/apache/parquet/column/values/bloomfilter/AdaptiveBlockSplitBloomFilter.java: ########## @@ -0,0 +1,307 @@ +/* + * 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.parquet.column.values.bloomfilter; + +import static org.apache.parquet.column.values.bloomfilter.BlockSplitBloomFilter.LOWER_BOUND_BYTES; +import static org.apache.parquet.column.values.bloomfilter.BlockSplitBloomFilter.UPPER_BOUND_BYTES; + +import java.io.IOException; +import java.io.OutputStream; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.List; +import java.util.Objects; +import java.util.Optional; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import org.apache.parquet.Preconditions; +import org.apache.parquet.column.ColumnDescriptor; +import org.apache.parquet.io.api.Binary; + +/** + * `AdaptiveBlockSplitBloomFilter` contains multiple `BlockSplitBloomFilter` as candidates and inserts values in + * the candidates at the same time. + * The purpose of this is to finally generate a bloom filter with the optimal bit size according to the number + * of real data distinct values. Use the largest bloom filter as an approximate deduplication counter, and then + * remove incapable bloom filter candidate during data insertion. + */ +public class AdaptiveBlockSplitBloomFilter implements BloomFilter { + + private static final Logger LOG = LoggerFactory.getLogger(AdaptiveBlockSplitBloomFilter.class); + + // multiple candidates, inserting data at the same time. If the distinct values are greater than the + // expected NDV of candidates, it will be removed. Finally we will choose the smallest candidate to write out. + private final List<BloomFilterCandidate> candidates = new ArrayList<>(); + + // the largest among candidates and used as an approximate deduplication counter + private BloomFilterCandidate largestCandidate; + + // the accumulator of the number of distinct values that have been inserted so far + private long distinctValueCounter = 0; + + // indicates that the bloom filter candidate has been written out and new data should be no longer allowed to be inserted + private boolean finalized = false; + + // indicates the step size to find the NDV value corresponding to numBytes + private static final int NDV_STEP = 500; + private int maximumBytes = UPPER_BOUND_BYTES; + private int minimumBytes = LOWER_BOUND_BYTES; + // the hash strategy used in this bloom filter. + private final HashStrategy hashStrategy; + // the column to build bloom filter + private ColumnDescriptor column; + + /** + * Given the maximum acceptable bytes size of bloom filter, generate candidates according it. + * + * @param maximumBytes the maximum bit size of candidate + * @param numCandidates the number of candidates + * @param fpp the false positive probability + */ + public AdaptiveBlockSplitBloomFilter(int maximumBytes, int numCandidates, double fpp, ColumnDescriptor column) { + this(maximumBytes, HashStrategy.XXH64, fpp, numCandidates, column); + } + + public AdaptiveBlockSplitBloomFilter(int maximumBytes, HashStrategy hashStrategy, double fpp, + int numCandidates, ColumnDescriptor column) { + this.column = column; + switch (hashStrategy) { + case XXH64: + this.hashStrategy = hashStrategy; + break; + default: + throw new RuntimeException("Unsupported hash strategy"); + } + initCandidates(maximumBytes, numCandidates, fpp); + } + + /** + * Given the maximum acceptable bytes size of bloom filter, generate candidates according + * to the bytes size. Because the bytes size of the candidate need to be a + * power of 2, we setting the candidate size according to `maxBytes` of `1/2`, `1/4`, `1/8`, etc. + * + * @param maxBytes the maximum bit size of candidate + * @param numCandidates the number of candidates + * @param fpp the false positive probability + */ + private void initCandidates(int maxBytes, int numCandidates, double fpp) { + int candidateByteSize = calculateBoundedPowerOfTwo(maxBytes); + for (int i = 1; i <= numCandidates; i++) { + int candidateExpectedNDV = expectedNDV(candidateByteSize, fpp); + // `candidateByteSize` is too small, just drop it + if (candidateExpectedNDV <= 0) { + break; + } + BloomFilterCandidate candidate = + new BloomFilterCandidate(candidateExpectedNDV, candidateByteSize, minimumBytes, maximumBytes, hashStrategy); + candidates.add(candidate); + candidateByteSize = calculateBoundedPowerOfTwo(candidateByteSize / 2); + } + Optional<BloomFilterCandidate> maxBloomFilter = candidates.stream().max(BloomFilterCandidate::compareTo); + if (maxBloomFilter.isPresent()) { + largestCandidate = maxBloomFilter.get(); + } else { + throw new IllegalArgumentException("`maximumBytes` is too small to create one valid bloom filter"); Review Comment: I agree with you, this shouldn't be a fatal error. However, in the ordinary bloom filter, no matter how small the bytes setting is, there will be a lower bound bloom filter generation (32 bytes size). So I modified it to have at least one minimum BloomFilter to align with the original implementation. How do you feel? -- 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]
