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Add cardinality estimator for key count estimation 

patch by yukim; reviewed by jbellis for CASSANDRA-5906
This commit is contained in:
Yuki Morishita 2013-12-20 13:57:28 -06:00
parent 4fb06b33d4
commit 642ce366d9
13 changed files with 307 additions and 21 deletions
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1
CHANGES.txt
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@ -18,6 +18,7 @@
* SSTable metadata(Stats.db) format change (CASSANDRA-6356)
* Push composites support in the storage engine (CASSANDRA-5417)
* Add snapshot space used to cfstats (CASSANDRA-6231)
* Add cardinality estimator for key count estimation (CASSANDRA-5906)
2.0.4

202
lib/licenses/stream-2.5.1.txt Normal file
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@ -0,0 +1,202 @@
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2
src/java/org/apache/cassandra/db/compaction/CompactionManager.java
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@ -550,7 +550,7 @@ public class CompactionManager implements CompactionManagerMBean
long totalkeysWritten = 0;
int expectedBloomFilterSize = Math.max(cfs.metadata.getIndexInterval(),
(int) (SSTableReader.getApproximateKeyCount(Arrays.asList(sstable), cfs.metadata)));
(int) (SSTableReader.getApproximateKeyCount(Arrays.asList(sstable))));
if (logger.isDebugEnabled())
logger.debug("Expected bloom filter size : {}", expectedBloomFilterSize);

2
src/java/org/apache/cassandra/db/compaction/CompactionTask.java
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@ -118,7 +118,7 @@ public class CompactionTask extends AbstractCompactionTask
long start = System.nanoTime();
long totalkeysWritten = 0;
long estimatedTotalKeys = Math.max(cfs.metadata.getIndexInterval(), SSTableReader.getApproximateKeyCount(actuallyCompact, cfs.metadata));
long estimatedTotalKeys = Math.max(cfs.metadata.getIndexInterval(), SSTableReader.getApproximateKeyCount(actuallyCompact));
long estimatedSSTables = Math.max(1, SSTableReader.getTotalBytes(actuallyCompact) / strategy.getMaxSSTableBytes());
long keysPerSSTable = (long) Math.ceil((double) estimatedTotalKeys / estimatedSSTables);
if (logger.isDebugEnabled())

2
src/java/org/apache/cassandra/db/compaction/Scrubber.java
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@ -85,7 +85,7 @@ public class Scrubber implements Closeable
? new ScrubController(cfs)
: new CompactionController(cfs, Collections.singleton(sstable), CompactionManager.getDefaultGcBefore(cfs));
this.isCommutative = cfs.metadata.getDefaultValidator().isCommutative();
this.expectedBloomFilterSize = Math.max(cfs.metadata.getIndexInterval(), (int)(SSTableReader.getApproximateKeyCount(toScrub,cfs.metadata)));
this.expectedBloomFilterSize = Math.max(cfs.metadata.getIndexInterval(), (int)(SSTableReader.getApproximateKeyCount(toScrub)));
// loop through each row, deserializing to check for damage.
// we'll also loop through the index at the same time, using the position from the index to recover if the

2
src/java/org/apache/cassandra/db/compaction/Upgrader.java
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@ -56,7 +56,7 @@ public class Upgrader
this.controller = new UpgradeController(cfs);
this.strategy = cfs.getCompactionStrategy();
long estimatedTotalKeys = Math.max(cfs.metadata.getIndexInterval(), SSTableReader.getApproximateKeyCount(toUpgrade, cfs.metadata));
long estimatedTotalKeys = Math.max(cfs.metadata.getIndexInterval(), SSTableReader.getApproximateKeyCount(toUpgrade));
long estimatedSSTables = Math.max(1, SSTableReader.getTotalBytes(this.toUpgrade) / strategy.getMaxSSTableBytes());
this.estimatedRows = (long) Math.ceil((double) estimatedTotalKeys / estimatedSSTables);
}

76
src/java/org/apache/cassandra/io/sstable/SSTableReader.java
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@ -20,16 +20,16 @@ package org.apache.cassandra.io.sstable;
import java.io.*;
import java.nio.ByteBuffer;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import com.clearspring.analytics.stream.cardinality.CardinalityMergeException;
import com.clearspring.analytics.stream.cardinality.ICardinality;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterators;
import com.google.common.collect.Ordering;
import com.google.common.primitives.Longs;
import com.google.common.util.concurrent.RateLimiter;
@ -46,7 +46,6 @@ import org.apache.cassandra.db.commitlog.ReplayPosition;
import org.apache.cassandra.db.compaction.ICompactionScanner;
import org.apache.cassandra.db.index.SecondaryIndex;
import org.apache.cassandra.dht.*;
import org.apache.cassandra.io.FSReadError;
import org.apache.cassandra.io.compress.CompressedRandomAccessReader;
import org.apache.cassandra.io.compress.CompressedThrottledReader;
import org.apache.cassandra.io.compress.CompressionMetadata;
@ -134,18 +133,69 @@ public class SSTableReader extends SSTable implements Closeable
public RestorableMeter readMeter;
private ScheduledFuture readMeterSyncFuture;
public static long getApproximateKeyCount(Iterable<SSTableReader> sstables, CFMetaData metadata)
/**
* Calculate approximate key count.
* If cardinality estimator is available on all given sstables, then this method use them to estimate
* key count.
* If not, then this uses index summaries.
*
* @param sstables SSTables to calculate key count
* @return estimated key count
*/
public static long getApproximateKeyCount(Collection<SSTableReader> sstables)
{
long count = 0;
long count = -1;
for (SSTableReader sstable : sstables)
// check if cardinality estimator is available for all SSTables
boolean cardinalityAvailable = !sstables.isEmpty() && Iterators.all(sstables.iterator(), new Predicate<SSTableReader>()
{
// using getMaxIndexSummarySize() lets us ignore the current sampling level
count += (sstable.getMaxIndexSummarySize() + 1) * sstable.indexSummary.getSamplingLevel();
if (logger.isDebugEnabled())
logger.debug("index size for bloom filter calc for file : {} : {}", sstable.getFilename(), count);
public boolean apply(SSTableReader sstable)
{
return sstable.descriptor.version.newStatsFile;
}
});
// if it is, load them to estimate key count
if (cardinalityAvailable)
{
boolean failed = false;
ICardinality cardinality = null;
for (SSTableReader sstable : sstables)
{
try
{
CompactionMetadata metadata = (CompactionMetadata) sstable.descriptor.getMetadataSerializer().deserialize(sstable.descriptor, MetadataType.COMPACTION);
if (cardinality == null)
cardinality = metadata.cardinalityEstimator;
else
cardinality = cardinality.merge(metadata.cardinalityEstimator);
}
catch (IOException e)
{
logger.warn("Reading cardinality from Statistics.db failed.", e);
failed = true;
break;
}
catch (CardinalityMergeException e)
{
logger.warn("Cardinality merge failed.", e);
failed = true;
break;
}
}
if (cardinality != null && !failed)
count = cardinality.cardinality();
}
// if something went wrong above or cardinality is not available, calculate using index summary
if (count < 0)
{
for (SSTableReader sstable : sstables)
{
// using getMaxIndexSummarySize() lets us ignore the current sampling level
count += (sstable.getMaxIndexSummarySize() + 1) * sstable.indexSummary.getSamplingLevel();
}
}
return count;
}

1
src/java/org/apache/cassandra/io/sstable/SSTableWriter.java
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@ -149,6 +149,7 @@ public class SSTableWriter extends SSTable
private void afterAppend(DecoratedKey decoratedKey, long dataPosition, RowIndexEntry index)
{
sstableMetadataCollector.addKey(decoratedKey.key);
lastWrittenKey = decoratedKey;
last = lastWrittenKey;
if (first == null)

15
src/java/org/apache/cassandra/io/sstable/metadata/CompactionMetadata.java
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@ -23,8 +23,12 @@ import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import com.clearspring.analytics.stream.cardinality.HyperLogLogPlus;
import com.clearspring.analytics.stream.cardinality.ICardinality;
import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.io.sstable.Descriptor;
import org.apache.cassandra.utils.ByteBufferUtil;
/**
* Compaction related SSTable metadata.
@ -37,9 +41,12 @@ public class CompactionMetadata extends MetadataComponent
public final Set<Integer> ancestors;
public CompactionMetadata(Set<Integer> ancestors)
public final ICardinality cardinalityEstimator;
public CompactionMetadata(Set<Integer> ancestors, ICardinality cardinalityEstimator)
{
this.ancestors = ancestors;
this.cardinalityEstimator = cardinalityEstimator;
}
public MetadataType getType()
@ -71,6 +78,8 @@ public class CompactionMetadata extends MetadataComponent
size += TypeSizes.NATIVE.sizeof(component.ancestors.size());
for (int g : component.ancestors)
size += TypeSizes.NATIVE.sizeof(g);
byte[] serializedCardinality = component.cardinalityEstimator.getBytes();
size += TypeSizes.NATIVE.sizeof(serializedCardinality.length) + serializedCardinality.length;
return size;
}
@ -79,6 +88,7 @@ public class CompactionMetadata extends MetadataComponent
out.writeInt(component.ancestors.size());
for (int g : component.ancestors)
out.writeInt(g);
ByteBufferUtil.writeWithLength(component.cardinalityEstimator.getBytes(), out);
}
public CompactionMetadata deserialize(Descriptor.Version version, DataInput in) throws IOException
@ -87,7 +97,8 @@ public class CompactionMetadata extends MetadataComponent
Set<Integer> ancestors = new HashSet<>(nbAncestors);
for (int i = 0; i < nbAncestors; i++)
ancestors.add(in.readInt());
return new CompactionMetadata(ancestors);
ICardinality cardinality = HyperLogLogPlus.Builder.build(ByteBufferUtil.readBytes(in, in.readInt()));
return new CompactionMetadata(ancestors, cardinality);
}
}
}

2
src/java/org/apache/cassandra/io/sstable/metadata/LegacyMetadataSerializer.java
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@ -148,7 +148,7 @@ public class LegacyMetadataSerializer extends MetadataSerializer
maxColumnNames));
if (types.contains(MetadataType.COMPACTION))
components.put(MetadataType.COMPACTION,
new CompactionMetadata(ancestors));
new CompactionMetadata(ancestors, null));
}
}
return components;

18
src/java/org/apache/cassandra/io/sstable/metadata/MetadataCollector.java
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@ -21,12 +21,15 @@ import java.io.File;
import java.nio.ByteBuffer;
import java.util.*;
import com.clearspring.analytics.stream.cardinality.HyperLogLogPlus;
import com.clearspring.analytics.stream.cardinality.ICardinality;
import com.google.common.collect.Maps;
import org.apache.cassandra.db.commitlog.ReplayPosition;
import org.apache.cassandra.db.composites.CellNameType;
import org.apache.cassandra.io.sstable.*;
import org.apache.cassandra.utils.EstimatedHistogram;
import org.apache.cassandra.utils.MurmurHash;
import org.apache.cassandra.utils.StreamingHistogram;
public class MetadataCollector
@ -77,6 +80,13 @@ public class MetadataCollector
protected int sstableLevel;
protected List<ByteBuffer> minColumnNames = Collections.emptyList();
protected List<ByteBuffer> maxColumnNames = Collections.emptyList();
/**
* Default cardinality estimation method is to use HyperLogLog++.
* Parameter here(p=13, sp=25) should give reasonable estimation
* while lowering bytes required to hold information.
* See CASSANDRA-5906 for detail.
*/
protected ICardinality cardinality = new HyperLogLogPlus(13, 25);
private final CellNameType columnNameComparator;
public MetadataCollector(CellNameType columnNameComparator)
@ -103,6 +113,12 @@ public class MetadataCollector
}
}
public void addKey(ByteBuffer key)
{
long hashed = MurmurHash.hash2_64(key, key.position(), key.remaining(), 0);
cardinality.offerHashed(hashed);
}
public void addRowSize(long rowSize)
{
estimatedRowSize.add(rowSize);
@ -213,7 +229,7 @@ public class MetadataCollector
sstableLevel,
minColumnNames,
maxColumnNames));
components.put(MetadataType.COMPACTION, new CompactionMetadata(ancestors));
components.put(MetadataType.COMPACTION, new CompactionMetadata(ancestors, cardinality));
return components;
}

5
src/java/org/apache/cassandra/tools/SSTableMetadataViewer.java
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@ -66,6 +66,11 @@ public class SSTableMetadataViewer
out.println(stats.replayPosition);
printHistograms(stats, out);
}
if (compaction != null)
{
out.printf("Ancestors: %s%n", compaction.ancestors.toString());
out.printf("Estimated cardinality: %s%n", compaction.cardinalityEstimator.cardinality());
}
}
}