/// <summary>
/// Merger Two Histograms
/// </summary>
/// <param name="curStatistics"></param>
/// <param name="newStatistics"></param>
/// <param name="currentJoin"></param>
/// <returns></returns>
internal static Statistics UpdateHistogram(Statistics curStatistics, Statistics newStatistics, out double joinSelectivity)
{
joinSelectivity = 1.0;
if (curStatistics == null)
return newStatistics;
else if (newStatistics == null)
return curStatistics;
var resHistogram = new Dictionary<long, Tuple<double, bool>>();
var curHistogram = curStatistics.Histogram;
var newHistogram = newStatistics.Histogram;
if (!curHistogram.Any())
{
return new Statistics
{
Density = newStatistics.Density,
Histogram = newHistogram,
};
}
if (!newHistogram.Any())
{
return new Statistics
{
Density = curStatistics.Density,
Histogram = curHistogram,
};
}
var curNotPopularCount = 0.0;
var newNotPopularCount = 0.0;
var curDefaultRow = curStatistics.Density * curStatistics.RowCount;
var newDefaultRow = newStatistics.Density * newStatistics.RowCount;
IEnumerator<KeyValuePair<long, Tuple<double, bool>>> newEntry = null;
bool fisrstMatch = false;
bool newHistogramEnd = false;
double resRowCount = 0.0;
List<long> notPopularValues = new List<long>();
foreach (var entry in curHistogram)
{
if (!fisrstMatch)
{
if (newHistogram.ContainsKey(entry.Key))
{
fisrstMatch = true;
var entry1 = entry;
newEntry = newHistogram.SkipWhile(e => e.Key != entry1.Key).GetEnumerator();
newEntry.MoveNext();
if (!entry.Value.Item2)
curNotPopularCount -= entry.Value.Item1;
if (!newEntry.Current.Value.Item2)
newNotPopularCount -= newEntry.Current.Value.Item1;
}
}
if (fisrstMatch)
{
if (newHistogramEnd || entry.Key < newEntry.Current.Key)
{
var curTuple = entry.Value;
if (curTuple.Item2 == true)
{
var tmpCount = curTuple.Item1 * newDefaultRow;
resRowCount += tmpCount;
resHistogram.Add(entry.Key, new Tuple<double, bool>(tmpCount, true));
}
else
{
notPopularValues.Add(entry.Key);
curNotPopularCount += curTuple.Item1;
resHistogram.Add(entry.Key, null);
}
}
else if (entry.Key > newEntry.Current.Key)
{
while (entry.Key > newEntry.Current.Key)
{
var newTuple = newEntry.Current.Value;
if (newTuple.Item2 == true)
{
var tmpCount = newTuple.Item1 * curDefaultRow;
resRowCount += tmpCount;
resHistogram.Add(newEntry.Current.Key, new Tuple<double, bool>(tmpCount, true));
}
else
{
notPopularValues.Add(newEntry.Current.Key);
newNotPopularCount += newTuple.Item1;
resHistogram.Add(newEntry.Current.Key, null);
}
if (!newEntry.MoveNext())
{
newHistogramEnd = true;
break;
}
}
if (newHistogramEnd)
{
break;
}
}
else
{
var curTuple = entry.Value;
var newTuple = newEntry.Current.Value;
if (curTuple.Item2 == false && newTuple.Item2 == false)
{
notPopularValues.Add(entry.Key);
curNotPopularCount += curTuple.Item1;
newNotPopularCount += newTuple.Item1;
resHistogram.Add(entry.Key, null);
}
else
{
var count1 = curTuple.Item2 ? curTuple.Item1 : curDefaultRow;
var count2 = newTuple.Item2 ? newTuple.Item1 : newDefaultRow;
var tmpCount = count1 * count2;
resRowCount += tmpCount;
resHistogram.Add(entry.Key, new Tuple<double, bool>(tmpCount, true));
}
if (!newEntry.MoveNext())
{
newHistogramEnd = true;
}
}
}
}
double density = -1;
if (notPopularValues.Any())
{
var resDefaultRow = curNotPopularCount * newNotPopularCount *
Math.Min(curDefaultRow / curNotPopularCount, newDefaultRow / newNotPopularCount);
resRowCount += resDefaultRow;
resDefaultRow = resDefaultRow / notPopularValues.Count;
density = resDefaultRow / resRowCount;
foreach (var value in notPopularValues)
{
resHistogram[value] = new Tuple<double, bool>(resDefaultRow, false);
}
}
joinSelectivity = resRowCount/(curStatistics.RowCount*newStatistics.RowCount);
return new Statistics
{
Histogram = resHistogram,
Density = density < 0 ? Math.Max(curStatistics.Density, newStatistics.Density) : density,
MaxValue = Math.Max(curStatistics.MaxValue, newStatistics.MaxValue),
RowCount = resRowCount,
};
}
/// <summary>
/// Updates the statistics histogram for the edge given the sink id list.
/// Bucket size is pre-defined
/// </summary>
/// <param name="edge"></param>
/// <param name="sinkList">sink id of the edge sampling</param>
internal static void UpdateEdgeHistogram(MatchEdge edge, List<long> sinkList)
{
sinkList.Sort();
var rowCount = sinkList.Count;
var statistics = new Statistics
{
RowCount = rowCount,
};
var height = (int)(rowCount / BucketNum);
var popBucketCount = 0;
var popValueCount = 0;
var bucketCount = 0;
// If number in each bucket is very small, then generate a Frequency Histogram
if (height < 2)
{
bucketCount = rowCount;
long preValue = sinkList[0];
int count = 1;
int distCount = 1;
for (int i = 1; i < rowCount; i++)
{
var curValue = sinkList[i];
if (curValue == preValue)
{
count++;
}
else
{
if (count > 1)
{
popBucketCount += count;
popValueCount++;
}
statistics.Histogram.Add(preValue, new Tuple<double, bool>(count, count > 1));
count = 1;
preValue = curValue;
distCount++;
}
}
if (count > 1)
{
popBucketCount += count;
popValueCount++;
}
statistics.Histogram.Add(preValue, new Tuple<double, bool>(count, count > 1));
statistics.MaxValue = preValue;
// Simple Denstity
//statistics.Density = 1.0 / distCount;
// Advanced Density
statistics.Density = bucketCount == popBucketCount
? 0
: 1.0 * (bucketCount - popBucketCount) / bucketCount / (distCount - popValueCount);
}
// Generates a Height-balanced Histogram
else
{
long preValue = sinkList[0];
int count = 0;
int distCount = 1;
for (int i = 1; i < rowCount; i++)
{
if (i % height == height - 1)
{
bucketCount++;
var curValue = sinkList[i];
if (curValue == preValue)
count += height;
else
{
distCount++;
if (count > height)
{
popBucketCount += count / height;
popValueCount++;
}
//count = count == 0 ? height : count;
statistics.Histogram.Add(preValue, new Tuple<double, bool>(count, count > height));
preValue = curValue;
count = height;
}
}
}
if (count > height)
{
popBucketCount += count / height;
popValueCount++;
}
statistics.Histogram.Add(preValue, new Tuple<double, bool>(count, count > height));
statistics.MaxValue = preValue;
// Simple Density
//statistics.Density = 1.0 / distCount;
// Advanced Density
statistics.Density = bucketCount == popBucketCount
? 0
: 1.0 * (bucketCount - popBucketCount) / bucketCount / (distCount - popValueCount);
}
edge.Statistics = statistics;
}
