cassandra-trunk/src/java/org/apache/cassandra/index/internal/composites/RegularColumnIndex.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.marshal.AbstractType;
import org.apache.cassandra.db.marshal.ByteBufferAccessor;
import org.apache.cassandra.db.rows.Cell;
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 REGULAR column definition on a composite type.
 *
 * 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 indexed if c_name == columnDef.name, and it will generate
 * (makeIndexColumnName()) an index entry whose:
 *   - row key will be the value v (getIndexedValue()).
 *   - cell name will
 *       rk ck_0 ... ck_n
 *     where rk is the row key of the initial cell. I.e. the index entry store
 *     all the information require to locate back the indexed cell.
 */
public class RegularColumnIndex extends CassandraIndex
{
    public RegularColumnIndex(ColumnFamilyStore baseCfs, IndexMetadata indexDef)
    {
        super(baseCfs, indexDef);
    }

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

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

        // Note: if indexing a static column, prefix will be Clustering.STATIC_CLUSTERING
        // so the Clustering obtained from builder::build will contain a value for only
        // the partition key. At query time though, this is all that's needed as the entire
        // base table partition should be returned for any mathching index entry.
        return builder;
    }

    public IndexEntry decodeEntry(DecoratedKey indexedValue, Row indexEntry)
    {
        Clustering<?> clustering = indexEntry.clustering();

        Clustering<?> indexedEntryClustering = null;
        if (getIndexedColumn().isStatic())
            indexedEntryClustering = Clustering.STATIC_CLUSTERING;
        else
        {
            ClusteringComparator baseComparator = baseCfs.getComparator();
            CBuilder builder = CBuilder.create(baseComparator);
            for (int i = 0; i < baseComparator.size(); i++)
                builder.add(clustering, i + 1);
            indexedEntryClustering = builder.build();
        }

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

    private static <V> boolean valueIsEqual(AbstractType<?> type, Cell<V> cell, ByteBuffer value)
    {
        return type.compare(cell.value(), cell.accessor(), value, ByteBufferAccessor.instance) == 0;
    }

    public boolean isStale(Row data, ByteBuffer indexValue, long nowInSec)
    {
        Cell<?> cell = data.getCell(indexedColumn);
        return cell == null
            || !cell.isLive(nowInSec)
            || !valueIsEqual(indexedColumn.type, cell, indexValue);
    }
}
