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   * Licensed to the Apache Software Foundation (ASF) under one
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   * 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
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   * See the License for the specific language governing permissions and
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  package org.apache.cassandra.tcm.listeners;
  
  import org.apache.cassandra.schema.KeyspaceMetadata;
  import org.apache.cassandra.service.StorageService;
  import org.apache.cassandra.tcm.ClusterMetadata;
  
  public class PlacementsChangeListener implements ChangeListener
  {
      @Override
      public void notifyPostCommit(ClusterMetadata prev, ClusterMetadata next, boolean fromSnapshot)
      {
          if (shouldInvalidate(prev, next))
              StorageService.instance.invalidateLocalRanges();
      }
  
      private boolean shouldInvalidate(ClusterMetadata prev, ClusterMetadata next)
      {
          if (!prev.placements.lastModified().equals(next.placements.lastModified()) &&
              !prev.placements.equivalentTo(next.placements)) // <- todo should we update lastModified if the result is the same?
              return true;
  
          if (prev.schema.getKeyspaces().size() != next.schema.getKeyspaces().size())
              return true;
  
          // can't rely only on placements alone since we can move a ks from rf=1 to rf=3 and the rf=3 params might already exist in the placements:
          for (KeyspaceMetadata ksm : prev.schema.getKeyspaces())
          {
              KeyspaceMetadata newKsm = next.schema.getKeyspaceMetadata(ksm.name);
              if (newKsm == null || !ksm.params.equals(newKsm.params))
                  return true;
          }
          return false;
      }
  }
  