What exactly is report grouping doing? (URGENT)

[Mark]

My report returns 1106 records in 00:00:00.01 of a second. This is the constant. I'm using C# and the MVC HTML5 viewer as such

@{
    var typeReportSource = new TypeReportSource() { TypeName = Model.ReportQualifiedAssemblyDetail };

    foreach (var parameter in Model.ReportData.Parameters)
    {
        typeReportSource.Parameters.Add(new Parameter(parameter.Name, parameter.Value));
    }

    @(Html.TelerikReporting().ReportViewer()
        .Id("ReportViewer")
        .ServiceUrl("/api/reporting/")
        .TemplateUrl("/ReportViewer/templates/CustomReportViewerTemplate.html")
        .ReportSource(typeReportSource)
        .ViewMode(ViewModes.PRINT_PREVIEW)
        .ScaleMode(ScaleModes.FIT_PAGE_WIDTH))
}

If I have no groups the report renders in 1.5 seconds with the following debug outputs (whatever they mean) 

*** ReportProcessor.ProcessReport STARTED ***

*** ProcessReport #0 STARTED ***
*** Report Processing STARTED ***
*** Report Processing DONE in 00:00:00.3665425 ***
*** ProcessReport #0 DONE in 00:00:00.3777970 ***

*** ReportProcessor.ProcessReport DONE in 00:00:00.3996569 ***
*** Get HTML5 Rendering Extension STARTED ***
*** Get HTML5 Rendering Extension DONE in 00:00:00.3654471 ***
*** RenderReport #0 STARTED ***
*** Measure Report STARTED ***
*** Measure Report STARTED ***
*** Measure Report STARTED ***
*** Measure Report DONE in 00:00:00.3463936 ***
*** Measure Report DONE in 00:00:00.3492620 ***
*** Measure Report DONE in 00:00:00.3523046 ***
*** Arrange Report STARTED ***
*** Arrange Report STARTED ***
*** Arrange Report STARTED ***
*** Arrange Report DONE in 00:00:00.0082247 ***
*** Arrange Report DONE in 00:00:00.0107413 ***
*** Arrange Report DONE in 00:00:00.0128169 ***

*** RenderReport #0 DONE in 00:00:01.5407080 ***

But, are we're talking a Kim Kardashian sized but here, if I put the three required groups on the report the report now takes 19 seconds before I even see the first page and it generates 12511 events in the debug window, so many in fact that I've included a paste bin URL for you

http://pastebin.com/rBv10mJw

The groups are headers only, i.e. hidden footers, they have a single text box on them and the group expression is a simple =Fields.WhatEverGroupFieldIsRequired

Also I've noticed that with or without groups my constructor is hit 3 times before it fetches data??

Can someone explain just what is happening and why it should take so long? Please, this is an urgent matter (I know I'm only on a trial license but please take pity on me I'm quite happy to sacrifice a goat or give over my first born if that will help??)

Mark

[Stef]

Hi Mark,

We tested the described scenario with the attached report definition. The time for processing and rendering did not change as in your description - approximately less than 2 seconds in both cases.

Check if you the data is the same in both tests or if there are any additional logic slowing down the processing. In addition, please test the report definition at your side. The constructor will normally be hit several times due to the instantiating of the report.

If you have further concerns, please open a support ticket and send us a runnable sample project illustrating the problem with the given times.

Regards,
Stef
Telerik