public override object Aggregate(int[] records, AggregateType kind)
{
bool hasData = false;
try
{
switch (kind)
{
case AggregateType.Sum:
decimal sum = s_defaultValue;
foreach (int record in records)
{
if (HasValue(record))
{
checked { sum += _values[record]; }
hasData = true;
}
}
if (hasData)
{
return sum;
}
return _nullValue;
case AggregateType.Mean:
decimal meanSum = s_defaultValue;
int meanCount = 0;
foreach (int record in records)
{
if (HasValue(record))
{
checked { meanSum += _values[record]; }
meanCount++;
hasData = true;
}
}
if (hasData)
{
decimal mean;
checked { mean = (meanSum / meanCount); }
return mean;
}
return _nullValue;
case AggregateType.Var:
case AggregateType.StDev:
int count = 0;
double var = (double)s_defaultValue;
double prec = (double)s_defaultValue;
double dsum = (double)s_defaultValue;
double sqrsum = (double)s_defaultValue;
foreach (int record in records)
{
if (HasValue(record))
{
dsum += (double)_values[record];
sqrsum += (double)_values[record] * (double)_values[record];
count++;
}
}
if (count > 1)
{
var = count * sqrsum - (dsum * dsum);
prec = var / (dsum * dsum);
// we are dealing with the risk of a cancellation error
// double is guaranteed only for 15 digits so a difference
// with a result less than 1e-15 should be considered as zero
if ((prec < 1e-15) || (var < 0))
var = 0;
else
var = var / (count * (count - 1));
if (kind == AggregateType.StDev)
{
return Math.Sqrt(var);
}
return var;
}
return _nullValue;
case AggregateType.Min:
decimal min = decimal.MaxValue;
for (int i = 0; i < records.Length; i++)
{
int record = records[i];
if (HasValue(record))
{
min = Math.Min(_values[record], min);
hasData = true;
}
}
if (hasData)
{
return min;
}
return _nullValue;
case AggregateType.Max:
decimal max = decimal.MinValue;
for (int i = 0; i < records.Length; i++)
{
int record = records[i];
if (HasValue(record))
{
max = Math.Max(_values[record], max);
hasData = true;
}
}
if (hasData)
{
return max;
}
return _nullValue;
case AggregateType.First:
if (records.Length > 0)
{
return _values[records[0]];
}
return null;
case AggregateType.Count:
return base.Aggregate(records, kind);
}
}
catch (OverflowException)
{
throw ExprException.Overflow(typeof(decimal));
}
throw ExceptionBuilder.AggregateException(kind, _dataType);
}