Fix empty struct type in selectNot call

api/src/main/java/org/apache/iceberg/types/GetProjectedIds.java

@@ -34,6 +34,11 @@ public Set<Integer> schema(Schema schema, Set<Integer> structResult) {
 
   @Override
   public Set<Integer> struct(Types.StructType struct, List<Set<Integer>> fieldResults) {
+    // if the struct is an empty struct, we should consider itself as 'internal', thus including its id.
+    if (struct.fields().size() == 0) {
+      // since returning null is signaling the call to field() to add the field ID.
+      return null;
+    }
     return fieldIds;
   }
 

api/src/main/java/org/apache/iceberg/types/TypeUtil.java

@@ -34,6 +34,7 @@
 import org.apache.iceberg.relocated.com.google.common.collect.Iterables;
 import org.apache.iceberg.relocated.com.google.common.collect.Lists;
 import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.relocated.com.google.common.collect.Sets;
 
 public class TypeUtil {
 
@@ -82,7 +83,11 @@ public static Set<Integer> getProjectedIds(Type type) {
   }
 
   private static Set<Integer> getIdsInternal(Type type) {
-    return visit(type, new GetProjectedIds());
+    Set<Integer> res = visit(type, new GetProjectedIds());
+    if (res == null) {
+      return Sets.newHashSet();
+    }
+    return res;
   }
 
   public static Types.StructType selectNot(Types.StructType struct, Set<Integer> fieldIds) {

api/src/test/java/org/apache/iceberg/types/TestTypeUtil.java

@@ -20,10 +20,13 @@
 
 package org.apache.iceberg.types;
 
+import java.util.Collections;
 import org.apache.iceberg.Schema;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableSet;
 import org.junit.Assert;
 import org.junit.Test;
 
+import static org.apache.iceberg.types.Types.NestedField.optional;
 import static org.apache.iceberg.types.Types.NestedField.required;
 
 
@@ -55,5 +58,26 @@ public void testValidateSchemaViaIndexByName() {
 
     TypeUtil.indexByName(Types.StructType.of(nestedType));
   }
+
+  @Test
+  public void testSelectNot() {
+    // iceberg schema which has an empty struct column.
+    Schema schema = new Schema(
+            required(1, "a", Types.IntegerType.get()),
+            optional(2, "b", Types.StructType.of(
+                    required(3, "c", Types.StringType.get()),
+                    optional(4, "d", Types.StructType.of(Collections.emptyList()))))
+    );
+    Schema filteredSchema = TypeUtil.selectNot(schema, ImmutableSet.of());
+    Assert.assertEquals(schema.toString(), filteredSchema.toString());
+
+    filteredSchema = TypeUtil.selectNot(schema, ImmutableSet.of(4));
+    Schema expected = new Schema(
+            required(1, "a", Types.IntegerType.get()),
+            optional(2, "b", Types.StructType.of(
+                    required(3, "c", Types.StringType.get())))
+    );
+    Assert.assertEquals(expected.toString(), filteredSchema.toString());
+  }
 }