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.db.rows;
  
  import org.apache.cassandra.db.DecoratedKey;
  import org.apache.cassandra.db.DeletionTime;
  import org.apache.cassandra.db.RegularAndStaticColumns;
  import org.apache.cassandra.schema.TableMetadata;
  import org.apache.cassandra.utils.AbstractIterator;
  
  /**
   * Abstract class to create UnfilteredRowIterator that lazily initializes itself.
   * <p>
   * This is used during partition range queries when we know the partition key but want
   * to defer the initialization of the rest of the UnfilteredRowIterator until we need it.
   */
  public abstract class LazilyInitializedUnfilteredRowIterator extends AbstractIterator<Unfiltered> implements UnfilteredRowIterator
  {
      private final DecoratedKey partitionKey;
  
      private UnfilteredRowIterator iterator;
  
      public LazilyInitializedUnfilteredRowIterator(DecoratedKey partitionKey)
      {
          this.partitionKey = partitionKey;
      }
  
      protected abstract UnfilteredRowIterator initializeIterator();
  
      protected void maybeInit()
      {
          if (iterator == null)
              iterator = initializeIterator();
      }
  
      public TableMetadata metadata()
      {
          maybeInit();
          return iterator.metadata();
      }
  
      public RegularAndStaticColumns columns()
      {
          maybeInit();
          return iterator.columns();
      }
  
      public boolean isReverseOrder()
      {
          maybeInit();
          return iterator.isReverseOrder();
      }
  
      public DecoratedKey partitionKey()
      {
          return partitionKey;
      }
  
      public DeletionTime partitionLevelDeletion()
      {
          maybeInit();
          return iterator.partitionLevelDeletion();
      }
  
      public Row staticRow()
      {
          maybeInit();
          return iterator.staticRow();
      }
  
      public EncodingStats stats()
      {
          maybeInit();
          return iterator.stats();
      }
  
      protected Unfiltered computeNext()
      {
          maybeInit();
          return iterator.hasNext() ? iterator.next() : endOfData();
      }
  
      public void close()
      {
          if (iterator != null)
          {
              iterator.close();
              iterator = null;
          }
      }
  
      public boolean isOpen()
      {
          return iterator != null;
      }
  }
  