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Merge pull request #86 from metamx/dimpartition-by-variance 

Select partition dimension by variance when cardinality is low
This commit is contained in:
cheddar 2013-02-13 09:54:34 -08:00
parent a0b159fed7 a665bfa2ef
commit 0eb65f69d4
1 changed files with 32 additions and 4 deletions
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36
indexer/src/main/java/com/metamx/druid/indexer/DeterminePartitionsJob.java
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@ -500,6 +500,7 @@ public class DeterminePartitionsJob implements Jobby
{
private static final double SHARD_COMBINE_THRESHOLD = 0.25;
private static final double SHARD_OVERSIZE_THRESHOLD = 1.5;
private static final int HIGH_CARDINALITY_THRESHOLD = 3000000;
@Override
protected void innerReduce(
@ -634,7 +635,9 @@ public class DeterminePartitionsJob implements Jobby
final int totalRows = dimPartitionss.values().iterator().next().getRows();
int maxCardinality = -1;
int maxCardinality = Integer.MIN_VALUE;
long minVariance = Long.MAX_VALUE;
DimPartitions minVariancePartitions = null;
DimPartitions maxCardinalityPartitions = null;
for(final DimPartitions dimPartitions : dimPartitionss.values()) {
@ -660,10 +663,18 @@ public class DeterminePartitionsJob implements Jobby
continue;
}
if(dimPartitions.getCardinality() > maxCardinality) {
maxCardinality = dimPartitions.getCardinality();
final int cardinality = dimPartitions.getCardinality();
final long variance = dimPartitions.getVariance();
if(cardinality > maxCardinality) {
maxCardinality = cardinality;
maxCardinalityPartitions = dimPartitions;
}
if(variance < minVariance) {
minVariance = variance;
minVariancePartitions = dimPartitions;
}
}
if(maxCardinalityPartitions == null) {
@ -675,8 +686,12 @@ public class DeterminePartitionsJob implements Jobby
context, config.makeSegmentPartitionInfoPath(new Bucket(0, bucket, 0)), config.isOverwriteFiles()
);
final DimPartitions chosenPartitions = maxCardinality > HIGH_CARDINALITY_THRESHOLD
? maxCardinalityPartitions
: minVariancePartitions;
final List<ShardSpec> chosenShardSpecs = Lists.transform(
maxCardinalityPartitions.partitions, new Function<DimPartition, ShardSpec>()
chosenPartitions.partitions, new Function<DimPartition, ShardSpec>()
{
@Override
public ShardSpec apply(DimPartition dimPartition)
@ -752,6 +767,19 @@ public class DeterminePartitionsJob implements Jobby
return sum;
}
public long getVariance()
{
final long meanRows = getRows() / partitions.size();
long variance = 0;
for(final DimPartition dimPartition : partitions) {
variance += (dimPartition.rows - meanRows) * (dimPartition.rows - meanRows);
}
variance /= partitions.size();
return variance;
}
public int getRows()
{
int sum = 0;