cassandra-trunk/src/java/org/apache/cassandra/index/internal/composites/ClusteringColumnIndex.java
/*
 * 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.index.internal.composites;

import java.nio.ByteBuffer;

import org.apache.cassandra.db.*;
import org.apache.cassandra.db.rows.CellPath;
import org.apache.cassandra.db.rows.Row;
import org.apache.cassandra.index.internal.CassandraIndex;
import org.apache.cassandra.index.internal.IndexEntry;
import org.apache.cassandra.schema.IndexMetadata;

/**
 * Index on a CLUSTERING_COLUMN column definition.
 *
 * A cell indexed by this index will have the general form:
 *   ck_0 ... ck_n c_name : v
 * where ck_i are the cluster keys, c_name the last component of the cell
 * composite name (or second to last if collections are in use, but this
 * has no impact) and v the cell value.
 *
 * Such a cell is always indexed by this index (or rather, it is indexed if
 * {@code 
 * n >= columnDef.componentIndex, which will always be the case in practice)
 * and it will generate (makeIndexColumnName()) an index entry whose:
 *   - row key will be ck_i (getIndexedValue()) where i == columnDef.componentIndex.
 *   - cell name will
 *       rk ck_0 ... ck_{i-1} ck_{i+1} ck_n
 *     where rk is the row key of the initial cell and i == columnDef.componentIndex.
 * }
 */
public class ClusteringColumnIndex extends CassandraIndex
{
    private final boolean enforceStrictLiveness;

    public ClusteringColumnIndex(ColumnFamilyStore baseCfs, IndexMetadata indexDef)
    {
        super(baseCfs, indexDef);
        this.enforceStrictLiveness = baseCfs.metadata.get().enforceStrictLiveness();
    }


    public ByteBuffer getIndexedValue(ByteBuffer partitionKey,
                                      Clustering<?> clustering,
                                      CellPath path, ByteBuffer cellValue)
    {
        return clustering.bufferAt(indexedColumn.position());
    }

    public <T> CBuilder buildIndexClusteringPrefix(ByteBuffer partitionKey,
                                                   ClusteringPrefix<T> prefix,
                                                   CellPath path)
    {
        CBuilder builder = CBuilder.create(getIndexComparator());
        builder.add(partitionKey);
        for (int i = 0; i < Math.min(indexedColumn.position(), prefix.size()); i++)
            builder.add(prefix.get(i), prefix.accessor());
        for (int i = indexedColumn.position() + 1; i < prefix.size(); i++)
            builder.add(prefix.get(i), prefix.accessor());
        return builder;
    }

    public IndexEntry decodeEntry(DecoratedKey indexedValue,
                                  Row indexEntry)
    {
        int ckCount = baseCfs.metadata().clusteringColumns().size();

        Clustering<?> clustering = indexEntry.clustering();
        CBuilder builder = CBuilder.create(baseCfs.getComparator());
        for (int i = 0; i < indexedColumn.position(); i++)
            builder.add(clustering, i + 1);

        builder.add(indexedValue.getKey());

        for (int i = indexedColumn.position() + 1; i < ckCount; i++)
            builder.add(clustering, i);

        return new IndexEntry(indexedValue,
                              clustering,
                              indexEntry.primaryKeyLivenessInfo().timestamp(),
                              clustering.bufferAt(0),
                              builder.build());
    }

    public boolean isStale(Row data, ByteBuffer indexValue, long nowInSec)
    {
        return !data.hasLiveData(nowInSec, enforceStrictLiveness);
    }
}
