public virtual object SelectAggregate(IDataQuery q, string name, IEnumerable <string> args)
{
name = name?.ToUpper() ?? throw new ArgumentNullException(nameof(name));
if (name != "COUNT" && name != "MIN" && name != "MAX" && name != "AVG" && name != "SUM" &&
name != "FIRST" && name != "LAST")
{
return(null);
}
var firstArg = args.FirstOrDefault();
// if COUNT with no or all selector, return Count
if (name == "COUNT" && (string.IsNullOrWhiteSpace(firstArg) || firstArg == "*"))
{
return(Count(q));
}
var query = InitQuery(q)
.ApplyConditions(q.Conditions);
object result;
if (name == "FIRST" || (name == "LAST" && !DataSourceSupportsLast))
{
if (q.OrderBy == null)
{
q.OrderByPrimaryKey();
}
var orderBy = q.OrderBy;
// if provider doesn't support Last, invert sort and pick first
if (name == "LAST")
{
for (var i = 0; i < q.OrderBy.OrderAsc.Length; i++)
{
orderBy.OrderAsc[i] = !q.OrderBy.OrderAsc[i];
}
}
query = query.ApplySorting(orderBy).ApplyLimits(q.Offset, q.Rows);
if (string.IsNullOrWhiteSpace(firstArg) || firstArg == "*")
{
result = query.FirstOrDefault();
}
else
{
result = query.Select(firstArg).FirstOrDefault();
}
}
else if (name == "LAST" && DataSourceSupportsLast)
{
query = query.ApplySorting(q.OrderBy).ApplyLimits(q.Offset, q.Rows);
if (string.IsNullOrWhiteSpace(firstArg) || firstArg == "*")
{
result = query.Last();
}
else
{
result = query.Select(firstArg).Last();
}
}
else
{
query = query
.ApplySorting(q.OrderBy)
.ApplyLimits(q.Offset, q.Rows);
if (q.OnlyFields != null && q.OnlyFields.Count > 0)
{
query.GroupBy(firstArg, string.Join(",", q.OnlyFields));
}
var n = (name == "AVG")
? "Average" // Method for AVG is Average
: name.ToPascalCase(); // ex. SUM => Sum (otherwise Method won't be found)
result = query.Aggregate(n, firstArg);
}
return(result);
}
