protected override Task MergeAsync(MergeContext context)
{
if (aggregation != null)
{
return(aggregation(context));
}
return(Task.CompletedTask);
}
protected override async Task ExecuteContextAsync(MethodContext context)
{
var groupResolver = (context as IContext).Scope.Resolve <IGroupResolver>();
if (groupResolver == null)
{
throw new NotSupportedException($"Aggregate function {MethodInfo.MethodName} requires a group resolver in context");
}
if (groupResolver.Size == 0)
{
context.SetResult(SqlObject.NullOf(MethodInfo.ReturnType));
return;
}
SqlExpression input = null;
if (context.ArgumentCount > 0)
{
input = context.Argument(0);
}
using (var seed = new InitializeContext(context, input)) {
await InitializeAsync(seed);
if (seed.Result != null)
{
input = seed.Result;
}
if (!seed.Iterate)
{
context.SetResult(input);
return;
}
}
SqlObject output = null;
if (input != null)
{
if (input is SqlReferenceExpression)
{
var reference = (SqlReferenceExpression)input;
output = await IterateReference(context, reference.ReferenceName, groupResolver);
}
else
{
output = await IterateValues(context, input, groupResolver);
}
}
using (var aggregate = new MergeContext(context, output)) {
await MergeAsync(aggregate);
if (aggregate.Output != null)
{
output = aggregate.Output;
}
}
context.SetResult(output);
}
protected virtual Task MergeAsync(MergeContext context)
{
return(Task.CompletedTask);
}