content: /*
   * 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.cassandra.service.pager;
  
  import java.nio.ByteBuffer;
  
  import org.apache.cassandra.db.*;
  import org.apache.cassandra.db.rows.*;
  import org.apache.cassandra.db.filter.*;
  import org.apache.cassandra.transport.ProtocolVersion;
  
  /**
   * Common interface to single partition queries (by slice and by name).
   *
   * For use by MultiPartitionPager.
   */
  public class SinglePartitionPager extends AbstractQueryPager<SinglePartitionReadQuery>
  {
      private volatile PagingState.RowMark lastReturned;
  
      public SinglePartitionPager(SinglePartitionReadQuery query, PagingState state, ProtocolVersion protocolVersion)
      {
          super(query, protocolVersion);
  
          if (state != null)
          {
              lastReturned = state.rowMark;
              restoreState(query.partitionKey(), state.remaining, state.remainingInPartition);
          }
      }
  
      private SinglePartitionPager(SinglePartitionReadQuery query,
                                   ProtocolVersion protocolVersion,
                                   PagingState.RowMark rowMark,
                                   int remaining,
                                   int remainingInPartition)
      {
          super(query, protocolVersion);
          this.lastReturned = rowMark;
          restoreState(query.partitionKey(), remaining, remainingInPartition);
      }
  
      @Override
      public SinglePartitionPager withUpdatedLimit(DataLimits newLimits)
      {
          return new SinglePartitionPager(query.withUpdatedLimit(newLimits),
                                          protocolVersion,
                                          lastReturned,
                                          maxRemaining(),
                                          remainingInPartition());
      }
  
      public ByteBuffer key()
      {
          return query.partitionKey().getKey();
      }
  
      public DataLimits limits()
      {
          return query.limits();
      }
  
      public PagingState state()
      {
          return lastReturned == null
               ? null
               : new PagingState(null, lastReturned, maxRemaining(), remainingInPartition());
      }
  
      @Override
      protected SinglePartitionReadQuery nextPageReadQuery(int pageSize)
      {
          Clustering<?> clustering = lastReturned == null ? null : lastReturned.clustering(query.metadata());
          DataLimits limits = lastReturned == null
                            ? limits().forPaging(pageSize)
                            : limits().forPaging(pageSize, key(), remainingInPartition());
  
          return query.forPaging(clustering, limits);
      }
  
      protected void recordLast(DecoratedKey key, Row last)
      {
          if (last != null && last.clustering() != Clustering.STATIC_CLUSTERING)
              lastReturned = PagingState.RowMark.create(query.metadata(), last, protocolVersion);
      }
  
      protected boolean isPreviouslyReturnedPartition(DecoratedKey key)
      {
          return lastReturned != null;
      }
  }
  