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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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,
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* See the License for the specific language governing permissions and
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*/
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> clusteringsInQueryOrder, boolean reversed);
}