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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.

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/*
 * 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.Arrays;

import com.google.common.annotations.VisibleForTesting;

import org.apache.cassandra.db.DeletionInfo;
import org.apache.cassandra.db.RegularAndStaticColumns;
import org.apache.cassandra.db.rows.EncodingStats;
import org.apache.cassandra.db.rows.Row;
import org.apache.cassandra.db.rows.Rows;
import org.apache.cassandra.utils.ObjectSizes;
import org.apache.cassandra.utils.btree.BTree;

/**
 * Holder of the content of a partition, see {@link AbstractBTreePartition}.
 * When updating a partition one holder is swapped for another atomically.
 */
public final class BTreePartitionData
{
    public static final BTreePartitionData EMPTY = new BTreePartitionData(RegularAndStaticColumns.NONE,
                                                                          BTree.empty(),
                                                                          DeletionInfo.LIVE,
                                                                          Rows.EMPTY_STATIC_ROW,
                                                                          EncodingStats.NO_STATS);
    public static final long UNSHARED_HEAP_SIZE = ObjectSizes.measure(EMPTY);


    final RegularAndStaticColumns columns;
    final DeletionInfo deletionInfo;
    // the btree of rows
    final Object[] tree;
    final Row staticRow;
    public final EncodingStats stats;

    BTreePartitionData(RegularAndStaticColumns columns,
                       Object[] tree,
                       DeletionInfo deletionInfo,
                       Row staticRow,
                       EncodingStats stats)
    {
        this.columns = columns;
        this.tree = tree;
        this.deletionInfo = deletionInfo;
        this.staticRow = staticRow == null ? Rows.EMPTY_STATIC_ROW : staticRow;
        this.stats = stats;
    }

    BTreePartitionData withColumns(RegularAndStaticColumns columns)
    {
        return new BTreePartitionData(columns, this.tree, this.deletionInfo, this.staticRow, this.stats);
    }

    @VisibleForTesting
    public static BTreePartitionData unsafeGetEmpty()
    {
        return EMPTY;
    }

    @VisibleForTesting
    public static BTreePartitionData unsafeConstruct(RegularAndStaticColumns columns,
                                                     Object[] tree,
                                                     DeletionInfo deletionInfo,
                                                     Row staticRow,
                                                     EncodingStats stats)
    {
        return new BTreePartitionData(columns, tree, deletionInfo, staticRow, stats);
    }

    @VisibleForTesting
    public static void unsafeInvalidate(AtomicBTreePartition partition)
    {
        BTreePartitionData holder = partition.unsafeGetHolder();
        if (!BTree.isEmpty(holder.tree))
        {
            partition.unsafeSetHolder(unsafeConstruct(holder.columns,
                                                      Arrays.copyOf(holder.tree, holder.tree.length),
                                                      holder.deletionInfo,
                                                      holder.staticRow,
                                                      holder.stats));
        }
    }
}