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.partitions;
  
  import java.util.NavigableSet;
  
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.schema.TableMetadata;
  import org.apache.cassandra.db.*;
  import org.apache.cassandra.db.rows.*;
  import org.apache.cassandra.db.filter.ColumnFilter;
  
  /**
   * In-memory representation of a Partition.
   *
   * Note that most of the storage engine works through iterators (UnfilteredPartitionIterator) to
   * avoid "materializing" a full partition/query response in memory as much as possible,
   * and so Partition objects should be use as sparingly as possible. There is a couple
   * of cases where we do need to represent partition in-memory (memtables and row cache).
   */
  public interface Partition
  {
      public TableMetadata metadata();
  
      public DecoratedKey partitionKey();
      public DeletionTime partitionLevelDeletion();
  
      public RegularAndStaticColumns columns();
  
      public EncodingStats stats();
  
      /**
       * Whether the partition object has no informations at all, including any deletion informations.
       */
      public boolean isEmpty();
  
      /**
       * Whether the partition object has rows. This may be false but partition still be non-empty if it has a deletion.
       */
      boolean hasRows();
  
      /**
       * Returns the row corresponding to the provided clustering, or null if there is not such row.
       *
       * @param clustering clustering key to search
       * @return row corresponding to the clustering, it's either null or non-empty row.
       */
      public @Nullable Row getRow(Clustering<?> clustering);
  
      /**
       * Returns an UnfilteredRowIterator over all the rows/RT contained by this partition.
       */
      public UnfilteredRowIterator unfilteredIterator();
  
      /**
       * Returns an UnfilteredRowIterator over the rows/RT contained by this partition
       * selected by the provided slices.
       */
      public UnfilteredRowIterator unfilteredIterator(ColumnFilter columns, Slices slices, boolean reversed);
  
      /**
       * Returns an UnfilteredRowIterator over the rows/RT contained by this partition
       * selected by the provided clusterings.
       */
      public UnfilteredRowIterator unfilteredIterator(ColumnFilter columns, NavigableSet<Clustering<?>> clusteringsInQueryOrder, boolean reversed);
  }
  