[GitHub] [iceberg] jackye1995 commented on a change in pull request #3983: Spark: Spark3 ZOrder Rewrite Strategy

[GitBox <gi...@apache.org>]

jackye1995 commented on a change in pull request #3983:
URL: https://github.com/apache/iceberg/pull/3983#discussion_r792400525



##########
File path: core/src/test/java/org/apache/iceberg/util/TestZOrderByteUtil.java
##########
@@ -0,0 +1,244 @@
+/*
+ * 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.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Random;
+import org.apache.commons.lang3.RandomStringUtils;
+import org.apache.iceberg.relocated.com.google.common.primitives.UnsignedBytes;
+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[]{
+        OOOOOOOO, OOOOOOOO, OOOOOOOO, OOOOIIII,
+        IOIOIOIO, IOIOIOIO,
+        OIOIOIOI, OIOIOIOI,
+        OOOOIIII};
+    Assert.assertArrayEquals("Should combine mixed byte arrays",
+        expected, ZOrderByteUtils.interleaveBits(test));
+  }
+
+  @Test
+  public void testIntOrdering() {
+    for (int i = 0; i < NUM_TESTS; i++) {
+      int aInt = random.nextInt();
+      int bInt = random.nextInt();
+      int intCompare = Integer.compare(aInt, bInt);
+      byte[] aBytes = ZOrderByteUtils.orderIntLikeBytes(bytesOf(aInt), 4);
+      byte[] bBytes = ZOrderByteUtils.orderIntLikeBytes(bytesOf(bInt), 4);
+      int byteCompare = UnsignedBytes.lexicographicalComparator().compare(aBytes, bBytes);
+
+      Assert.assertTrue(String.format(
+          "Ordering of ints should match ordering of bytes, %s ~ %s -> %s != %s ~ %s -> %s ",
+          aInt, bInt, intCompare, Arrays.toString(aBytes), Arrays.toString(bBytes), byteCompare),
+          (intCompare ^ byteCompare) >= 0);
+    }
+  }
+
+  @Test
+  public void testLongOrdering() {
+    for (int i = 0; i < NUM_TESTS; i++) {
+      long aLong = random.nextInt();
+      long bLong = random.nextInt();
+      int longCompare = Long.compare(aLong, bLong);
+      byte[] aBytes = ZOrderByteUtils.orderIntLikeBytes(bytesOf(aLong), 8);
+      byte[] bBytes = ZOrderByteUtils.orderIntLikeBytes(bytesOf(bLong), 8);
+      int byteCompare = UnsignedBytes.lexicographicalComparator().compare(aBytes, bBytes);
+
+      Assert.assertTrue(String.format(
+          "Ordering of ints should match ordering of bytes, %s ~ %s -> %s != %s ~ %s -> %s ",

Review comment:
       nit: ordering of longs, same issue for all other data type tests

##########
File path: api/src/main/java/org/apache/iceberg/actions/RewriteDataFiles.java
##########
@@ -113,6 +113,15 @@ default RewriteDataFiles sort(SortOrder sortOrder) {
     throw new UnsupportedOperationException("SORT Rewrite Strategy not implemented for this framework");
   }
 
+  /**
+   * Choose Z-ORDER as a strategy for this rewrite operation with a specified list of columns to use
+   * @param columns Columns to be used to generate Z-Values
+   * @return this for method chaining
+   */
+  default RewriteDataFiles zOrder(String... columns) {

Review comment:
       I remember in the original design zOrder is considered a part of the sort order, so it makes more sense to me for the input here to be `SortOrder` instead of `String... columns`. I guess this will be a shortcut for something like `SortOrder.builderFor(schema).zOrder().columns(a,b,c).bitWidth(10)` when that interface is out? But how do people define things like string column width to cutoff in this case?

##########
File path: spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/actions/Spark3ZOrderStrategy.java
##########
@@ -0,0 +1,249 @@
+/*
+ * 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.spark.actions;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.FileScanTask;
+import org.apache.iceberg.NullOrder;
+import org.apache.iceberg.PartitionField;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.SortDirection;
+import org.apache.iceberg.Table;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.spark.FileRewriteCoordinator;
+import org.apache.iceberg.spark.FileScanTaskSetManager;
+import org.apache.iceberg.spark.SparkDistributionAndOrderingUtil;
+import org.apache.iceberg.spark.SparkReadOptions;
+import org.apache.iceberg.spark.SparkWriteOptions;
+import org.apache.iceberg.types.Types;
+import org.apache.iceberg.types.Types.NestedField;
+import org.apache.iceberg.util.SortOrderUtil;
+import org.apache.iceberg.util.ZOrderByteUtils;
+import org.apache.spark.sql.Column;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan;
+import org.apache.spark.sql.connector.distributions.Distribution;
+import org.apache.spark.sql.connector.distributions.Distributions;
+import org.apache.spark.sql.connector.expressions.SortOrder;
+import org.apache.spark.sql.expressions.UserDefinedFunction;
+import org.apache.spark.sql.functions;
+import org.apache.spark.sql.internal.SQLConf;
+import org.apache.spark.sql.types.BinaryType;
+import org.apache.spark.sql.types.BooleanType;
+import org.apache.spark.sql.types.ByteType;
+import org.apache.spark.sql.types.DataType;
+import org.apache.spark.sql.types.DataTypes;
+import org.apache.spark.sql.types.DateType;
+import org.apache.spark.sql.types.DoubleType;
+import org.apache.spark.sql.types.FloatType;
+import org.apache.spark.sql.types.IntegerType;
+import org.apache.spark.sql.types.LongType;
+import org.apache.spark.sql.types.ShortType;
+import org.apache.spark.sql.types.StringType;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.types.TimestampType;
+import scala.collection.Seq;
+
+public class Spark3ZOrderStrategy extends Spark3SortStrategy {
+  private static final String Z_COLUMN = "ICEZVALUE";
+  private static final Schema Z_SCHEMA = new Schema(NestedField.required(0, Z_COLUMN, Types.BinaryType.get()));
+  private static final org.apache.iceberg.SortOrder Z_SORT_ORDER = org.apache.iceberg.SortOrder.builderFor(Z_SCHEMA)
+      .sortBy(Z_COLUMN, SortDirection.ASC, NullOrder.NULLS_LAST)
+      .build();
+  private static final int STRING_KEY_LENGTH = 60;

Review comment:
       I see, going back to the top question, this is currently static. Can we at least make this configurable somehow, maybe as a part of the interface input?




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