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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,
* 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.rows;
import java.nio.ByteBuffer;
import java.util.*;
import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.config.ColumnDefinition;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.context.CounterContext;
import org.apache.cassandra.db.filter.ColumnFilter;
public class SerializationHelper
{
/**
* Flag affecting deserialization behavior (this only affect counters in practice).
* - LOCAL: for deserialization of local data (Expired columns are
* converted to tombstones (to gain disk space)).
* - FROM_REMOTE: for deserialization of data received from remote hosts
* (Expired columns are converted to tombstone and counters have
* their delta cleared)
* - PRESERVE_SIZE: used when no transformation must be performed, i.e,
* when we must ensure that deserializing and reserializing the
* result yield the exact same bytes. Streaming uses this.
*/
public enum Flag
{
LOCAL, FROM_REMOTE, PRESERVE_SIZE
}
private final Flag flag;
public final int version;
private final ColumnFilter columnsToFetch;
private ColumnFilter.Tester tester;
private final Map droppedColumns;
private CFMetaData.DroppedColumn currentDroppedComplex;
public SerializationHelper(CFMetaData metadata, int version, Flag flag, ColumnFilter columnsToFetch)
{
this.flag = flag;
this.version = version;
this.columnsToFetch = columnsToFetch;
this.droppedColumns = metadata.getDroppedColumns();
}
public SerializationHelper(CFMetaData metadata, int version, Flag flag)
{
this(metadata, version, flag, null);
}
public Columns fetchedStaticColumns(SerializationHeader header)
{
return columnsToFetch == null ? header.columns().statics : columnsToFetch.fetchedColumns().statics;
}
public Columns fetchedRegularColumns(SerializationHeader header)
{
return columnsToFetch == null ? header.columns().regulars : columnsToFetch.fetchedColumns().regulars;
}
public boolean includes(ColumnDefinition column)
{
return columnsToFetch == null || columnsToFetch.includes(column);
}
public boolean includes(CellPath path)
{
return path == null || tester == null || tester.includes(path);
}
public boolean canSkipValue(ColumnDefinition column)
{
return columnsToFetch != null && columnsToFetch.canSkipValue(column);
}
public boolean canSkipValue(CellPath path)
{
return path != null && tester != null && tester.canSkipValue(path);
}
public void startOfComplexColumn(ColumnDefinition column)
{
this.tester = columnsToFetch == null ? null : columnsToFetch.newTester(column);
this.currentDroppedComplex = droppedColumns.get(column.name.bytes);
}
public void endOfComplexColumn()
{
this.tester = null;
}
public boolean isDropped(Cell cell, boolean isComplex)
{
CFMetaData.DroppedColumn dropped = isComplex ? currentDroppedComplex : droppedColumns.get(cell.column().name.bytes);
return dropped != null && cell.timestamp() <= dropped.droppedTime;
}
public boolean isDroppedComplexDeletion(DeletionTime complexDeletion)
{
return currentDroppedComplex != null && complexDeletion.markedForDeleteAt() <= currentDroppedComplex.droppedTime;
}
public ByteBuffer maybeClearCounterValue(ByteBuffer value)
{
return flag == Flag.FROM_REMOTE || (flag == Flag.LOCAL && CounterContext.instance().shouldClearLocal(value))
? CounterContext.instance().clearAllLocal(value)
: value;
}
}