LuciferYang commented on code in PR #56740: URL: https://github.com/apache/spark/pull/56740#discussion_r3467943984
########## common/kvstore/src/test/java/org/apache/spark/util/kvstore/DBIteratorCompareSuite.java: ########## @@ -0,0 +1,67 @@ +/* + * 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.spark.util.kvstore; + +import org.junit.jupiter.api.Test; +import static org.junit.jupiter.api.Assertions.*; + +/** + * Unit tests for the static byte-array comparator that LevelDBIterator and RocksDBIterator + * each define (the two backends are kept independent, so the method is duplicated). The + * comparator is pure and needs no database, so these tests run on every platform. + */ +public class DBIteratorCompareSuite { + + @FunctionalInterface + private interface ByteArrayComparator { + int compare(byte[] a, byte[] b); + } + + @Test + public void testLevelDBIteratorCompare() { + checkUnsignedByteOrdering(LevelDBIterator::compare); + } + + @Test + public void testRocksDBIteratorCompare() { + checkUnsignedByteOrdering(RocksDBIterator::compare); + } + + private static void checkUnsignedByteOrdering(ByteArrayComparator cmp) { + // Equal arrays compare equal. + assertEquals(0, cmp.compare(new byte[] { 1, 2, 3 }, new byte[] { 1, 2, 3 })); + + // A prefix sorts before the longer array that extends it. + assertTrue(cmp.compare(new byte[] { 1, 2 }, new byte[] { 1, 2, 3 }) < 0); + assertTrue(cmp.compare(new byte[] { 1, 2, 3 }, new byte[] { 1, 2 }) > 0); + + // Bytes must be ordered as unsigned, matching the underlying key ordering: 0x80 (128) is + // greater than 0x7f (127). A signed comparison would wrongly treat 0x80 as -128. + byte[] highBit = new byte[] { (byte) 0x80 }; + byte[] lowBit = new byte[] { 0x7f }; + assertTrue(cmp.compare(highBit, lowBit) > 0); + assertTrue(cmp.compare(lowBit, highBit) < 0); + + // 0xff (255) is the largest byte value when unsigned, so it sorts after 0x00. + assertTrue(cmp.compare(new byte[] { (byte) 0xff }, new byte[] { 0x00 }) > 0); + + // The first differing byte decides the order, regardless of later bytes. + assertTrue(cmp.compare(new byte[] { 0x01, (byte) 0xff }, new byte[] { 0x02, 0x00 }) < 0); + } + Review Comment: Good idea, added compare({}, {}), compare({}, {1}), and the symmetric compare({1}, {}). -- 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]
