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* Licensed to the Apache Software Foundation (ASF) under one
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* 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
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package org.apache.cassandra.db.compaction;
import java.io.DataOutput;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.security.MessageDigest;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import com.google.common.base.Predicates;
import com.google.common.collect.Iterators;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.columniterator.OnDiskAtomIterator;
import org.apache.cassandra.db.index.SecondaryIndexManager;
import org.apache.cassandra.io.sstable.ColumnNameHelper;
import org.apache.cassandra.io.sstable.ColumnStats;
import org.apache.cassandra.io.sstable.SSTable;
import org.apache.cassandra.io.sstable.SSTableWriter;
import org.apache.cassandra.io.util.DataOutputBuffer;
import org.apache.cassandra.utils.MergeIterator;
import org.apache.cassandra.utils.StreamingHistogram;
/**
* LazilyCompactedRow only computes the row bloom filter and column index in memory
* (at construction time); it does this by reading one column at a time from each
* of the rows being compacted, and merging them as it does so. So the most we have
* in memory at a time is the bloom filter, the index, and one column from each
* pre-compaction row.
*/
public class LazilyCompactedRow extends AbstractCompactedRow
{
private final List<? extends OnDiskAtomIterator> rows;
private final CompactionController controller;
private final long maxPurgeableTimestamp;
private final ColumnFamily emptyColumnFamily;
private ColumnStats columnStats;
private boolean closed;
private ColumnIndex.Builder indexBuilder;
private final SecondaryIndexManager.Updater indexer;
private final Reducer reducer;
private final Iterator<OnDiskAtom> merger;
private DeletionTime maxRowTombstone;
public LazilyCompactedRow(CompactionController controller, List<? extends OnDiskAtomIterator> rows)
{
super(rows.get(0).getKey());
this.rows = rows;
this.controller = controller;
indexer = controller.cfs.indexManager.updaterFor(key);
// Combine top-level tombstones, keeping the one with the highest markedForDeleteAt timestamp. This may be
// purged (depending on gcBefore), but we need to remember it to properly delete columns during the merge
maxRowTombstone = DeletionTime.LIVE;
for (OnDiskAtomIterator row : rows)
{
DeletionTime rowTombstone = row.getColumnFamily().deletionInfo().getTopLevelDeletion();
if (maxRowTombstone.compareTo(rowTombstone) < 0)
maxRowTombstone = rowTombstone;
}
// tombstones with a localDeletionTime before this can be purged. This is the minimum timestamp for any sstable
// containing `key` outside of the set of sstables involved in this compaction.
maxPurgeableTimestamp = controller.maxPurgeableTimestamp(key);
emptyColumnFamily = EmptyColumns.factory.create(controller.cfs.metadata);
emptyColumnFamily.delete(maxRowTombstone);
if (maxRowTombstone.markedForDeleteAt < maxPurgeableTimestamp)
emptyColumnFamily.purgeTombstones(controller.gcBefore);
reducer = new Reducer();
merger = Iterators.filter(MergeIterator.get(rows, emptyColumnFamily.getComparator().onDiskAtomComparator(), reducer), Predicates.notNull());
}
private static void removeDeleted(ColumnFamily cf, boolean shouldPurge, DecoratedKey key, CompactionController controller)
{
// We should only purge cell tombstones if shouldPurge is true, but regardless, it's still ok to remove cells that
// are shadowed by a row or range tombstone; removeDeletedColumnsOnly(cf, Integer.MIN_VALUE) will accomplish this
// without purging tombstones.
int overriddenGCBefore = shouldPurge ? controller.gcBefore : Integer.MIN_VALUE;
ColumnFamilyStore.removeDeletedColumnsOnly(cf, overriddenGCBefore, controller.cfs.indexManager.updaterFor(key));
}
public RowIndexEntry write(long currentPosition, DataOutput out) throws IOException
{
assert !closed;
ColumnIndex columnsIndex;
try
{
indexBuilder = new ColumnIndex.Builder(emptyColumnFamily, key.key, out);
columnsIndex = indexBuilder.buildForCompaction(merger);
// if there aren't any columns or tombstones, return null
if (columnsIndex.columnsIndex.isEmpty() && !emptyColumnFamily.isMarkedForDelete())
return null;
}
catch (IOException e)
{
throw new RuntimeException(e);
}
// reach into the reducer (created during iteration) to get column count, size, max column timestamp
columnStats = new ColumnStats(reducer.columns,
reducer.minTimestampSeen,
Math.max(emptyColumnFamily.deletionInfo().maxTimestamp(), reducer.maxTimestampSeen),
reducer.maxLocalDeletionTimeSeen,
reducer.tombstones,
reducer.minColumnNameSeen,
reducer.maxColumnNameSeen
);
// in case no columns were ever written, we may still need to write an empty header with a top-level tombstone
indexBuilder.maybeWriteEmptyRowHeader();
out.writeShort(SSTableWriter.END_OF_ROW);
close();
return RowIndexEntry.create(currentPosition, emptyColumnFamily.deletionInfo().getTopLevelDeletion(), columnsIndex);
}
public void update(MessageDigest digest)
{
assert !closed;
// no special-case for rows.size == 1, we're actually skipping some bytes here so just
// blindly updating everything wouldn't be correct
DataOutputBuffer out = new DataOutputBuffer();
try
{
DeletionTime.serializer.serialize(emptyColumnFamily.deletionInfo().getTopLevelDeletion(), out);
digest.update(out.getData(), 0, out.getLength());
}
catch (IOException e)
{
throw new AssertionError(e);
}
// initialize indexBuilder for the benefit of its tombstoneTracker, used by our reducing iterator
indexBuilder = new ColumnIndex.Builder(emptyColumnFamily, key.key, out);
while (merger.hasNext())
merger.next().updateDigest(digest);
close();
}
public ColumnStats columnStats()
{
return columnStats;
}
public void close()
{
for (OnDiskAtomIterator row : rows)
{
try
{
row.close();
}
catch (IOException e)
{
throw new RuntimeException(e);
}
}
closed = true;
}
private class Reducer extends MergeIterator.Reducer<OnDiskAtom, OnDiskAtom>
{
// all columns reduced together will have the same name, so there will only be one column
// in the container; we just want to leverage the conflict resolution code from CF.
// (Note that we add the row tombstone in getReduced.)
final ColumnFamily container = ArrayBackedSortedColumns.factory.create(emptyColumnFamily.metadata());
// tombstone reference; will be reconciled w/ column during getReduced. Note that the top-level (row) tombstone
// is held by LCR.deletionInfo.
RangeTombstone tombstone;
int columns = 0;
long minTimestampSeen = Long.MAX_VALUE;
long maxTimestampSeen = Long.MIN_VALUE;
int maxLocalDeletionTimeSeen = Integer.MIN_VALUE;
StreamingHistogram tombstones = new StreamingHistogram(SSTable.TOMBSTONE_HISTOGRAM_BIN_SIZE);
List<ByteBuffer> minColumnNameSeen = Collections.emptyList();
List<ByteBuffer> maxColumnNameSeen = Collections.emptyList();
/**
* Called once per version of a cell that we need to merge, after which getReduced() is called. In other words,
* this will be called one or more times with cells that share the same column name.
*/
public void reduce(OnDiskAtom current)
{
if (current instanceof RangeTombstone)
{
if (tombstone == null || current.maxTimestamp() >= tombstone.maxTimestamp())
tombstone = (RangeTombstone)current;
}
else
{
Cell cell = (Cell) current;
container.addColumn(cell);
// skip the index-update checks if there is no indexing needed since they are a bit expensive
if (indexer == SecondaryIndexManager.nullUpdater)
return;
if (!cell.isMarkedForDelete(System.currentTimeMillis())
&& !container.getColumn(cell.name()).equals(cell))
{
indexer.remove(cell);
}
}
}
/**
* Called after reduce() has been called for each cell sharing the same name.
*/
protected OnDiskAtom getReduced()
{
if (tombstone != null)
{
RangeTombstone t = tombstone;
tombstone = null;
if (t.data.isGcAble(controller.gcBefore))
{
return null;
}
else
{
return t;
}
}
else
{
boolean shouldPurge = container.getSortedColumns().iterator().next().timestamp() < maxPurgeableTimestamp;
// when we clear() the container, it removes the deletion info, so this needs to be reset each time
container.delete(maxRowTombstone);
removeDeleted(container, shouldPurge, key, controller);
Iterator<Cell> iter = container.iterator();
if (!iter.hasNext())
{
container.clear();
return null;
}
Cell reduced = iter.next();
container.clear();
// removeDeleted have only checked the top-level CF deletion times,
// not the range tombstone. For that we use the columnIndexer tombstone tracker.
if (indexBuilder.tombstoneTracker().isDeleted(reduced))
{
indexer.remove(reduced);
return null;
}
columns++;
minTimestampSeen = Math.min(minTimestampSeen, reduced.minTimestamp());
maxTimestampSeen = Math.max(maxTimestampSeen, reduced.maxTimestamp());
maxLocalDeletionTimeSeen = Math.max(maxLocalDeletionTimeSeen, reduced.getLocalDeletionTime());
minColumnNameSeen = ColumnNameHelper.minComponents(minColumnNameSeen, reduced.name(), controller.cfs.metadata.comparator);
maxColumnNameSeen = ColumnNameHelper.maxComponents(maxColumnNameSeen, reduced.name(), controller.cfs.metadata.comparator);
int deletionTime = reduced.getLocalDeletionTime();
if (deletionTime < Integer.MAX_VALUE)
{
tombstones.update(deletionTime);
}
return reduced;
}
}
}
}