uschindler commented on a change in pull request #446: URL: https://github.com/apache/lucene/pull/446#discussion_r757160246
########## File path: lucene/sandbox/src/java/org/apache/lucene/sandbox/index/MergeOnFlushTieredMergePolicy.java ########## @@ -0,0 +1,138 @@ +/* + * 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.index; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.List; +import org.apache.lucene.index.MergeTrigger; +import org.apache.lucene.index.SegmentCommitInfo; +import org.apache.lucene.index.SegmentInfos; +import org.apache.lucene.index.TieredMergePolicy; + +/** + * A simple extension to {@link TieredMergePolicy} to merge all tiny segments (or at least segments + * smaller than specified in setSmallSegmentThresholdMB) into one segment on commit. + */ +public class MergeOnFlushTieredMergePolicy extends TieredMergePolicy { + private double maxSegmentSizeAsProportionOfIndex = 1.0; + private long smallSegmentThresholdBytes = Units.mbToBytes(100.0); + private long hardMaxSegmentSizeBytes = 5 * 1024 * 1024 * 1024L; + + private static long indexSize(SegmentInfos infos) throws IOException { + long totalSize = 0; + for (SegmentCommitInfo sci : infos) { + totalSize += sci.sizeInBytes(); + } + return totalSize; + } + + public double getSmallSegmentThresholdMB() { + return Units.bytesToMB(smallSegmentThresholdBytes); + } + + /** + * @param smallSegmentThresholdMB all segments smaller than this will be merged into a single + * segment before commit completes. + */ + public void setSmallSegmentThresholdMB(double smallSegmentThresholdMB) { + this.smallSegmentThresholdBytes = Units.mbToBytes(smallSegmentThresholdMB); + } + + public double getMaxSegmentSizeAsProportionOfIndex() { + return maxSegmentSizeAsProportionOfIndex; + } + + public void setMaxSegmentSizeAsProportionOfIndex(double maxSegmentSizeAsProportionOfIndex) { + if (maxSegmentSizeAsProportionOfIndex < 0.0 || maxSegmentSizeAsProportionOfIndex > 1.0) { + throw new IllegalArgumentException( + "maxSegmentSizeAsProportionOfIndex must be between 0 and 1; got: " + + maxSegmentSizeAsProportionOfIndex); + } + this.maxSegmentSizeAsProportionOfIndex = maxSegmentSizeAsProportionOfIndex; + } + + @Override + public TieredMergePolicy setMaxMergedSegmentMB(double v) { + this.hardMaxSegmentSizeBytes = Units.mbToBytes(v); + return this; + } + + @Override + public MergeSpecification findMerges( + MergeTrigger mergeTrigger, SegmentInfos infos, MergeContext mergeContext) throws IOException { + double maxSegmentSizeMB = + Units.bytesToMB( + Math.min( + hardMaxSegmentSizeBytes, + Math.max( + Units.mbToBytes(getFloorSegmentMB()), + (long) (getMaxSegmentSizeAsProportionOfIndex() * indexSize(infos))))); + super.setMaxMergedSegmentMB(maxSegmentSizeMB); + return super.findMerges(mergeTrigger, excludeSmallSegments(infos), mergeContext); + } + + /** + * Returns a SegmentInfos with all segments smaller than smallSegmentThresholdBytes removed. + * + * @param realSegmentInfos the "real", unfiltered {@link SegmentInfos} + * @return a new {@link SegmentInfos} instance containing all {@link SegmentCommitInfo} from + * realSegmentInfos that are at least as large as smallSegmentThresholdBytes. + * @throws IOException if unable to load the size of a {@link SegmentCommitInfo} + */ + private SegmentInfos excludeSmallSegments(SegmentInfos realSegmentInfos) throws IOException { + SegmentInfos largeSegmentInfos = + new SegmentInfos(realSegmentInfos.getIndexCreatedVersionMajor()); + for (SegmentCommitInfo sci : realSegmentInfos.asList()) { + if (sci.sizeInBytes() >= smallSegmentThresholdBytes) { + largeSegmentInfos.add(sci); + } + } + return largeSegmentInfos; + } + + @Override + public MergeSpecification findFullFlushMerges( + MergeTrigger mergeTrigger, SegmentInfos segmentInfos, MergeContext mergeContext) + throws IOException { + List<SegmentCommitInfo> smallSegments = new ArrayList<>(); + for (SegmentCommitInfo sci : segmentInfos) { + if (sci.sizeInBytes() < smallSegmentThresholdBytes) { + if (mergeContext.getMergingSegments().contains(sci) == false) { + smallSegments.add(sci); + } + } + } + if (smallSegments.size() > 1) { + MergeSpecification mergeSpecification = new MergeSpecification(); + mergeSpecification.add(new OneMerge(smallSegments)); + return mergeSpecification; + } + return null; + } + /** Utility class to handle conversion between megabytes and bytes */ + public static class Units { Review comment: I think PKG protected (no access modifier) is better. 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