"Show Generated SQL" takes a really long time

[cccschip]

I use the "Show Generated SQL" tool a lot during development and debugging of reports.  But we have a report now which takes a very, very long time (as in 2 hours) to get a response.  Seriously, I click the option in the Tools menu and wait for 2 hours before it finally presents me the prompt page where I can supply the parameter values to complete the query definition.  I then specify the parameter value, click OK, and the SQL is generated shortly afterwards.

What could possibly be causing this behavior?  I have not seen it in other reports.

The particular report is a list of accumulated values (mostly sums) with grouping over 3 columns.  Nothing very special, in my opinion.

[Lynn]

Are any of the filters looking at a fact table query item to render a pick list for one of your parameters? The engine would need to do a select distinct to present the choices and that might cause the behavior.

[cccschip]

I am very sorry for the lack of followup...thought I had marked this as Notify, but apparently not.

Lynn is, of course, right.  There was a pick-list prompt involved which was doing a scan across a very large fact set.

Our bad.

[Lynn]

...
Lynn is, of course, right. 
...

8)

This is not always the case so I will bask in my moment of glory!