Core: Support unpartitioned specs in SortOrderUtil (apache#2239)

core/src/main/java/org/apache/iceberg/util/SortOrderUtil.java

@@ -37,16 +37,14 @@ private SortOrderUtil() {
   }
 
   public static SortOrder buildSortOrder(Table table) {
-    return buildSortOrder(table.spec(), table.sortOrder());
+    return buildSortOrder(table.schema(), table.spec(), table.sortOrder());
   }
 
-  public static SortOrder buildSortOrder(PartitionSpec spec, SortOrder sortOrder) {
+  static SortOrder buildSortOrder(Schema schema, PartitionSpec spec, SortOrder sortOrder) {
     if (sortOrder.isUnsorted() && spec.isUnpartitioned()) {
       return SortOrder.unsorted();
     }
 
-    Schema schema = spec.schema();
-
     Multimap<Integer, SortField> sortFieldIndex = Multimaps.index(sortOrder.fields(), SortField::sourceId);
 
     // build a sort prefix of partition fields that are not already in the sort order

core/src/test/java/org/apache/iceberg/util/TestSortOrderUtil.java

@@ -0,0 +1,94 @@
+/*
+ * 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.io.File;
+import java.io.IOException;
+import org.apache.iceberg.PartitionSpec;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.SortOrder;
+import org.apache.iceberg.TestTables;
+import org.apache.iceberg.types.Types;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import static org.apache.iceberg.NullOrder.NULLS_LAST;
+import static org.apache.iceberg.SortDirection.ASC;
+import static org.apache.iceberg.types.Types.NestedField.required;
+
+@RunWith(Parameterized.class)
+public class TestSortOrderUtil {
+
+  // column ids will be reassigned during table creation
+  private static final Schema SCHEMA = new Schema(
+      required(10, "id", Types.IntegerType.get()),
+      required(11, "data", Types.StringType.get())
+  );
+
+  @Rule
+  public TemporaryFolder temp = new TemporaryFolder();
+  private File tableDir = null;
+
+  @Parameterized.Parameters(name = "formatVersion = {0}")
+  public static Object[] parameters() {
+    return new Object[] { 1, 2 };
+  }
+
+  private final int formatVersion;
+
+  public TestSortOrderUtil(int formatVersion) {
+    this.formatVersion = formatVersion;
+  }
+
+  @Before
+  public void setupTableDir() throws IOException {
+    this.tableDir = temp.newFolder();
+  }
+
+  @After
+  public void cleanupTables() {
+    TestTables.clearTables();
+  }
+
+  @Test
+  public void testEmptySpecs() {
+    PartitionSpec spec = PartitionSpec.unpartitioned();
+    SortOrder order = SortOrder.builderFor(SCHEMA)
+        .withOrderId(1)
+        .asc("id", NULLS_LAST)
+        .build();
+    TestTables.TestTable table = TestTables.create(tableDir, "test", SCHEMA, spec, order, formatVersion);
+
+    // pass PartitionSpec.unpartitioned() on purpose as it has an empty schema
+    SortOrder actualOrder = SortOrderUtil.buildSortOrder(table.schema(), spec, table.sortOrder());
+
+    Assert.assertEquals("Order ID must be fresh", 1, actualOrder.orderId());
+    Assert.assertEquals("Order must have 1 field", 1, actualOrder.fields().size());
+    Assert.assertEquals("Field id must be fresh", 1, actualOrder.fields().get(0).sourceId());
+    Assert.assertEquals("Direction must match", ASC, actualOrder.fields().get(0).direction());
+    Assert.assertEquals("Null order must match", NULLS_LAST, actualOrder.fields().get(0).nullOrder());
+  }
+}