tkalkirill commented on code in PR #6601: URL: https://github.com/apache/ignite-3/pull/6601#discussion_r2355833175
########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = + AtomicReferenceFieldUpdater.newUpdater(SegmentInfo.class, int[].class, "segmentFileOffsets"); + + private static final int INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY = 10; + + /** + * Base log index. All log indexes in the memtable are relative to this value. + */ + private final long logIndexBase; + + /** + * Offsets in a segment file. + */ + private volatile int[] segmentFileOffsets = new int[INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY]; + + /** + * Number of entries in the {@link #segmentFileOffsets} array. + * + * <p>Multi-threaded visibility is guaranteed by volatile reads or writes to the {@link #segmentFileOffsets} field. + */ + private int segmentFileOffsetSize = 0; + + SegmentInfo(long logIndexBase) { + this.logIndexBase = logIndexBase; + } + + void addOffset(long logIndex, int segmentFileOffset) { + int[] originalSegmentFileOffsets = this.segmentFileOffsets; + + int[] segmentFileOffsets = originalSegmentFileOffsets; + + // Check that log indexes are monotonically increasing. + assert segmentFileOffsetSize == logIndex - logIndexBase; + + if (segmentFileOffsets.length == segmentFileOffsetSize) { + segmentFileOffsets = Arrays.copyOf(segmentFileOffsets, segmentFileOffsets.length * 2); Review Comment: Now I'm wondering if 2x is too much? Maybe 1.5x is better, like in standard collections? -- 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: notifications-unsubscr...@ignite.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
