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Posted to issues@iceberg.apache.org by GitBox <gi...@apache.org> on 2022/02/07 16:51:27 UTC
[GitHub] [iceberg] findepi commented on a change in pull request #3966: Core: Adds Utility Class for Implementing ZOrdering
findepi commented on a change in pull request #3966:
URL: https://github.com/apache/iceberg/pull/3966#discussion_r800853640
##########
File path: core/src/main/java/org/apache/iceberg/util/ZOrderByteUtils.java
##########
@@ -0,0 +1,162 @@
+/*
+ * 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.nio.ByteBuffer;
+import java.util.Arrays;
+
+/**
+ * Within Z-Ordering the byte representations of objects being compared must be ordered,
+ * this requires several types to be transformed when converted to bytes. The goal is to
+ * map object's whose byte representation are not lexicographically ordered into representations
+ * that are lexicographically ordered.
+ * Most of these techniques are derived from
+ * https://aws.amazon.com/blogs/database/z-order-indexing-for-multifaceted-queries-in-amazon-dynamodb-part-2/
+ *
+ * Some implementation is taken from
+ * https://github.com/apache/hbase/blob/master/hbase-common/src/main/java/org/apache/hadoop/hbase/util/OrderedBytes.java
+ */
+public class ZOrderByteUtils {
+
+ private ZOrderByteUtils() {
+
+ }
+
+ /**
+ * Signed ints do not have their bytes in magnitude order because of the sign bit.
+ * To fix this, flip the sign bit so that all negatives are ordered before positives. This essentially
+ * shifts the 0 value so that we don't break our ordering when we cross the new 0 value.
+ */
+ public static byte[] intToOrderedBytes(int val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Integer.BYTES);
+ bytes.putInt(val ^ 0x80000000);
+ return bytes.array();
+ }
+
+ /**
+ * Signed longs are treated the same as the signed ints
+ */
+ public static byte[] longToOrderBytes(long val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Long.BYTES);
+ bytes.putLong(val ^ 0x8000000000000000L);
+ return bytes.array();
+ }
+
+ /**
+ * Signed shorts are treated the same as the signed ints
+ */
+ public static byte[] shortToOrderBytes(short val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Short.BYTES);
+ bytes.putShort((short) (val ^ (0x8000)));
+ return bytes.array();
+ }
+
+ /**
+ * Signed tiny ints are treated the same as the signed ints
+ */
+ public static byte[] tinyintToOrderedBytes(byte val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Byte.BYTES);
+ bytes.put((byte) (val ^ (0x80)));
+ return bytes.array();
+ }
+
+ /**
+ * IEEE 754 :
+ * “If two floating-point numbers in the same format are ordered (say, x {@literal <} y),
+ * they are ordered the same way when their bits are reinterpreted as sign-magnitude integers.”
+ *
+ * Which means floats can be treated as sign magnitude integers which can then be converted into lexicographically
+ * comparable bytes
+ */
+ public static byte[] floatToOrderedBytes(float val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Integer.BYTES);
+ int ival = Float.floatToIntBits(val);
+ ival ^= ((ival >> (Integer.SIZE - 1)) | Integer.MIN_VALUE);
+ bytes.putInt(ival);
+ return bytes.array();
+ }
+
+ /**
+ * Doubles are treated the same as floats
+ */
+ public static byte[] doubleToOrderedBytes(double val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Long.BYTES);
+ long lng = Double.doubleToLongBits(val);
+ lng ^= ((lng >> (Long.SIZE - 1)) | Long.MIN_VALUE);
+ bytes.putLong(lng);
+ return bytes.array();
+ }
+
+ /**
+ * Strings are lexicographically sortable BUT if different byte array lengths will
+ * ruin the Z-Ordering. (ZOrder requires that a given column contribute the same number of bytes every time).
+ * This implementation just uses a set size to for all output byte representations. Truncating longer strings
+ * and right padding 0 for shorter strings.
+ */
+ public static byte[] stringToOrderedBytes(String val, int length) {
+ ByteBuffer bytes = ByteBuffer.allocate(length);
+ if (val != null) {
+ int maxLength = Math.min(length, val.length());
+ bytes.put(val.getBytes(), 0, maxLength);
Review comment:
The encoding must be fixed, and it must be UTF-8.
Also byte order will match string/varchar order only if bytes are treated as unsigned.
I guess he unsignedness applies to other types, so maybe it's documented already, i didn't notice.
##########
File path: core/src/main/java/org/apache/iceberg/util/ZOrderByteUtils.java
##########
@@ -0,0 +1,162 @@
+/*
+ * 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.nio.ByteBuffer;
+import java.util.Arrays;
+
+/**
+ * Within Z-Ordering the byte representations of objects being compared must be ordered,
+ * this requires several types to be transformed when converted to bytes. The goal is to
+ * map object's whose byte representation are not lexicographically ordered into representations
+ * that are lexicographically ordered.
+ * Most of these techniques are derived from
+ * https://aws.amazon.com/blogs/database/z-order-indexing-for-multifaceted-queries-in-amazon-dynamodb-part-2/
+ *
+ * Some implementation is taken from
+ * https://github.com/apache/hbase/blob/master/hbase-common/src/main/java/org/apache/hadoop/hbase/util/OrderedBytes.java
+ */
+public class ZOrderByteUtils {
+
+ private ZOrderByteUtils() {
+
+ }
+
+ /**
+ * Signed ints do not have their bytes in magnitude order because of the sign bit.
+ * To fix this, flip the sign bit so that all negatives are ordered before positives. This essentially
+ * shifts the 0 value so that we don't break our ordering when we cross the new 0 value.
+ */
+ public static byte[] intToOrderedBytes(int val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Integer.BYTES);
+ bytes.putInt(val ^ 0x80000000);
+ return bytes.array();
+ }
+
+ /**
+ * Signed longs are treated the same as the signed ints
+ */
+ public static byte[] longToOrderBytes(long val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Long.BYTES);
+ bytes.putLong(val ^ 0x8000000000000000L);
+ return bytes.array();
+ }
+
+ /**
+ * Signed shorts are treated the same as the signed ints
+ */
+ public static byte[] shortToOrderBytes(short val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Short.BYTES);
+ bytes.putShort((short) (val ^ (0x8000)));
+ return bytes.array();
+ }
+
+ /**
+ * Signed tiny ints are treated the same as the signed ints
+ */
+ public static byte[] tinyintToOrderedBytes(byte val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Byte.BYTES);
+ bytes.put((byte) (val ^ (0x80)));
+ return bytes.array();
+ }
+
+ /**
+ * IEEE 754 :
+ * “If two floating-point numbers in the same format are ordered (say, x {@literal <} y),
+ * they are ordered the same way when their bits are reinterpreted as sign-magnitude integers.”
+ *
+ * Which means floats can be treated as sign magnitude integers which can then be converted into lexicographically
+ * comparable bytes
+ */
+ public static byte[] floatToOrderedBytes(float val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Integer.BYTES);
+ int ival = Float.floatToIntBits(val);
+ ival ^= ((ival >> (Integer.SIZE - 1)) | Integer.MIN_VALUE);
+ bytes.putInt(ival);
+ return bytes.array();
+ }
+
+ /**
+ * Doubles are treated the same as floats
+ */
+ public static byte[] doubleToOrderedBytes(double val) {
+ ByteBuffer bytes = ByteBuffer.allocate(Long.BYTES);
+ long lng = Double.doubleToLongBits(val);
+ lng ^= ((lng >> (Long.SIZE - 1)) | Long.MIN_VALUE);
+ bytes.putLong(lng);
+ return bytes.array();
+ }
+
+ /**
+ * Strings are lexicographically sortable BUT if different byte array lengths will
+ * ruin the Z-Ordering. (ZOrder requires that a given column contribute the same number of bytes every time).
+ * This implementation just uses a set size to for all output byte representations. Truncating longer strings
+ * and right padding 0 for shorter strings.
+ */
+ public static byte[] stringToOrderedBytes(String val, int length) {
+ ByteBuffer bytes = ByteBuffer.allocate(length);
+ if (val != null) {
+ int maxLength = Math.min(length, val.length());
Review comment:
`val.length()` is not "encoding-aware". Maybe add a comment that it doesn't matter.
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