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   * 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
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  package org.apache.cassandra.db.tries;
  
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  import java.util.Random;
  import java.util.SortedMap;
  import java.util.TreeMap;
  
  import org.junit.Test;
  
  import org.apache.cassandra.utils.bytecomparable.ByteComparable;
  
  import static org.apache.cassandra.db.tries.InMemoryTrieTestBase.*;
  
  public class MergeTrieTest
  {
      private static final int COUNT = 15000;
      Random rand = new Random();
  
      @Test
      public void testDirect()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
  
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          content1.putAll(content2);
          Trie<ByteBuffer> union = trie1.mergeWith(trie2, (x, y) -> x);
  
          assertSameContent(union, content1);
      }
  
      @Test
      public void testWithDuplicates()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
  
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          addToInMemoryTrie(generateKeys(new Random(5), COUNT), content1, trie1, true);
          addToInMemoryTrie(generateKeys(new Random(5), COUNT), content2, trie2, true);
  
          content1.putAll(content2);
          Trie<ByteBuffer> union = trie1.mergeWith(trie2, (x, y) -> y);
  
          assertSameContent(union, content1);
      }
  
      @Test
      public void testDistinct()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
  
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          src2 = removeDuplicates(src2, content1);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          content1.putAll(content2);
          Trie<ByteBuffer> union = new MergeTrie.Distinct<>(trie1, trie2);
  
          assertSameContent(union, content1);
      }
  
      static ByteComparable[] removeDuplicates(ByteComparable[] keys, SortedMap<ByteComparable, ByteBuffer> content1)
      {
          return Arrays.stream(keys)
                       .filter(key -> !content1.containsKey(key))
                       .toArray(ByteComparable[]::new);
      }
  }
  