RussellSpitzer commented on a change in pull request #3966: URL: https://github.com/apache/iceberg/pull/3966#discussion_r801135964
########## File path: core/src/test/java/org/apache/iceberg/util/TestZOrderByteUtil.java ########## @@ -0,0 +1,260 @@ +/* + * 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.iceberg.util; + +import java.util.Arrays; +import java.util.Random; +import org.apache.iceberg.relocated.com.google.common.primitives.UnsignedBytes; +import org.apache.iceberg.types.Types; +import org.junit.Assert; +import org.junit.Test; + +public class TestZOrderByteUtil { + private static final byte IIIIIIII = (byte) 255; + private static final byte IOIOIOIO = (byte) 170; + private static final byte OIOIOIOI = (byte) 85; + private static final byte OOOOIIII = (byte) 15; + private static final byte OOOOOOOI = (byte) 1; + private static final byte OOOOOOOO = (byte) 0; + + private static final int NUM_TESTS = 100000; + + private final Random random = new Random(42); + + private String bytesToString(byte[] bytes) { + StringBuilder result = new StringBuilder(); + for (byte b : bytes) { + result.append(String.format("%8s", Integer.toBinaryString(b & 0xFF)).replace(' ', '0')); + } + return result.toString(); + } + + /** + * Returns a non-0 length byte array + */ + private byte[] generateRandomBytes() { + int length = Math.abs(random.nextInt(100) + 1); + byte[] result = new byte[length]; + random.nextBytes(result); + return result; + } + + /** + * Test method to ensure correctness of byte interleaving code + */ + private String interleaveStrings(String[] strings) { + StringBuilder result = new StringBuilder(); + int totalLength = Arrays.stream(strings).mapToInt(String::length).sum(); + int substringIndex = 0; + int characterIndex = 0; + while (characterIndex < totalLength) { + for (String str : strings) { + if (substringIndex < str.length()) { + result.append(str.charAt(substringIndex)); + characterIndex++; + } + } + substringIndex++; + } + return result.toString(); + } + + /** + * Compares the result of a string based interleaving algorithm implemented above + * versus the binary bit-shifting algorithm used in ZOrderByteUtils. Either both + * algorithms are identically wrong or are both identically correct. + */ + @Test + public void testInterleaveRandomExamples() { + for (int test = 0; test < NUM_TESTS; test++) { + int numByteArrays = Math.abs(random.nextInt(6)) + 1; + byte[][] testBytes = new byte[numByteArrays][]; + String[] testStrings = new String[numByteArrays]; + for (int byteIndex = 0; byteIndex < numByteArrays; byteIndex++) { + testBytes[byteIndex] = generateRandomBytes(); + testStrings[byteIndex] = bytesToString(testBytes[byteIndex]); + } + byte[] byteResult = ZOrderByteUtils.interleaveBits(testBytes); + String byteResultAsString = bytesToString(byteResult); + + String stringResult = interleaveStrings(testStrings); + + Assert.assertEquals("String interleave didn't match byte interleave", stringResult, byteResultAsString); + } + } + + @Test + public void testInterleaveEmptyBits() { + byte[][] test = new byte[4][10]; + byte[] expected = new byte[40]; + + Assert.assertArrayEquals("Should combine empty arrays", + expected, ZOrderByteUtils.interleaveBits(test)); + } + + @Test + public void testInterleaveFullBits() { + byte[][] test = new byte[4][]; + test[0] = new byte[]{IIIIIIII, IIIIIIII}; + test[1] = new byte[]{IIIIIIII}; + test[2] = new byte[0]; + test[3] = new byte[]{IIIIIIII, IIIIIIII, IIIIIIII}; + byte[] expected = new byte[]{IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII}; + + Assert.assertArrayEquals("Should combine full arrays", + expected, ZOrderByteUtils.interleaveBits(test)); + } + + @Test + public void testInterleaveMixedBits() { + byte[][] test = new byte[4][]; + test[0] = new byte[]{OOOOOOOI, IIIIIIII, OOOOOOOO, OOOOIIII}; + test[1] = new byte[]{OOOOOOOI, OOOOOOOO, IIIIIIII}; + test[2] = new byte[]{OOOOOOOI}; + test[3] = new byte[]{OOOOOOOI}; + byte[] expected = new byte[]{ Review comment: I think a good way to do this may be to change the api slightly to ```java public static byte[] interleaveBits(byte[][] columnsBinary) { return interleaveBits(columnsBinary, Arrays.stream(columnsBinary).mapToInt(column -> column.length).max().getAsInt()); } /** * Interleave bits using a naive loop. Variable length inputs are allowed but to get a consistent ordering it is * required that every column contribute the same number of bytes in each invocation. Bits are interleaved from all * columns that have a bit available at that position. Once a Column has no more bits to produce it is skipped in the * interleaving. * @param columnsBinary an array of ordered byte representations of the columns being ZOrdered * @param interleavedSize the number of bytes to use in the output * @return the columnbytes interleaved */ public static byte[] interleaveBits(byte[][] columnsBinary, int interleavedSize) { ``` So that instead of calculating the output-size, the caller can just pass in the number of bytes it wants out of the algorithm. This handles bailing out earlier as well as not allocating as much. I can leave the original signature for the test suite. -- This is an automated message from the Apache Git Service. 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