public override object Aggregate(int[] records, AggregateType kind)
{
bool hasData = false;
try
{
switch (kind)
{
case AggregateType.Sum:
SqlInt64 sum = 0;
foreach (int record in records)
{
if (IsNull(record))
continue;
checked { sum += _values[record]; }
hasData = true;
}
if (hasData)
{
return sum;
}
return _nullValue;
case AggregateType.Mean:
SqlDecimal meanSum = 0;
int meanCount = 0;
foreach (int record in records)
{
if (IsNull(record))
continue;
checked { meanSum += _values[record].ToSqlDecimal(); }
meanCount++;
hasData = true;
}
if (hasData)
{
SqlInt64 mean = 0;
checked { mean = (meanSum / meanCount).ToSqlInt64(); }
return mean;
}
return _nullValue;
case AggregateType.Var:
case AggregateType.StDev:
int count = 0;
SqlDouble var = 0;
SqlDouble prec = 0;
SqlDouble dsum = 0;
SqlDouble sqrsum = 0;
foreach (int record in records)
{
if (IsNull(record))
continue;
dsum += (_values[record]).ToSqlDouble();
sqrsum += (_values[record]).ToSqlDouble() * (_values[record]).ToSqlDouble();
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.Value);
}
return var;
}
return _nullValue;
case AggregateType.Min:
SqlInt64 min = SqlInt64.MaxValue;
for (int i = 0; i < records.Length; i++)
{
int record = records[i];
if (IsNull(record))
continue;
if ((SqlInt64.LessThan(_values[record], min)).IsTrue)
min = _values[record];
hasData = true;
}
if (hasData)
{
return min;
}
return _nullValue;
case AggregateType.Max:
SqlInt64 max = SqlInt64.MinValue;
for (int i = 0; i < records.Length; i++)
{
int record = records[i];
if (IsNull(record))
continue;
if ((SqlInt64.GreaterThan(_values[record], max)).IsTrue)
max = _values[record];
hasData = true;
}
if (hasData)
{
return max;
}
return _nullValue;
case AggregateType.First:
if (records.Length > 0)
{
return _values[records[0]];
}
return null;// no data => null
case AggregateType.Count:
count = 0;
for (int i = 0; i < records.Length; i++)
{
if (!IsNull(records[i]))
count++;
}
return count;
}
}
catch (OverflowException)
{
throw ExprException.Overflow(typeof(SqlInt64));
}
throw ExceptionBuilder.AggregateException(kind, _dataType);
}