Postback takes a LONG time! -- sql server reporting services

Brian Hartman [MSFT]
9/30/2004 6:19:35 PM

The server can not determine the dependencies between parameters when some
of them are expressions, so it is conservative and assumes that a dependency
exists. When you navigate away from the text box (to another text box or to
the view report button), the page posts back to get new defaults and valid
values for downstream parameters. If there is no dependency, you can
reorder the parameters to prevent the post back. A parmeter can only depend
on parameters that came before it. So if you make your expression based
parameter the last one, there will be no auto post back.

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rdcpro
9/30/2004 7:09:02 PM

Thanks Brian,

This particular control is the last parameter, but there is also a select
box that is the second-to-last parameter. This one uses a default value, but
not an expression. In particular, it has a set of values that look like

Label Value
foo 0
bar 1
snafu 2

and the default value is specified as:

0

and not

=0

In this case, a postback shouldn't occur, because this is not an expression
but a scalar value, right?

And even if it were an expression, while the server doesn't know if there is
a dependancy, the Designer (me) knows. It seems to me that when I design a
report with parameters that use expressions, I should have a checkbox to
disable postback or declaratively state there is no dependancy.

Any thoughts?

Thanks again,
Mike

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rdcpro
10/1/2004 12:19:08 PM

In case others run into this issue, I wanted to post my resolution.

At issue is the fact that a report parameter with an expression is assumed
to be dependant on another report parameter, even when in fact it's only
dependant on a global value or even if it simply uses an expression to return
a scalar result. So, when you set a default value using an expression, the
control is "disabled" and there is no way for the user to physically set the
control without first entering a fake value in another field, then causing a
postback to "refresh" the parameter. Only then can the user set the value
for the parameter using an expression. Of course, before the user runs the
query he/she must remove the "fake" value.

In my case, a user might enter a date in my "End Date" field, then click
"View Report". Instead of actually seeing the report, the screen blanks, a
postback occurs, and it appears to the user that either nothing happened, or
the report returned no results. They have to click "View Report" again to
get the report to run.

Evidently, the behavior is "by design" inasmuch as RS isn't smart enough to
realize there is no dependancy for this parameter, and there is no way in the
report designer to declaratively state as much.

In my case, I simply wanted to set the default value of the parameter to
"true" in one folder, and "false" in another. My solution was to use the
same approach that creating a linked report would use. Upload the report
with no default value on the control, then in the Report Manager, manually
specify the default value I want (either true or false) in the Properties >
Parameters page.

It would be really nice if there was a similar option in the Report
Designer, or if you could set the default to a scalar value directly the same
way you can for a drop-down parameter!

Hope this helps someone,
Mike

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sql server reporting services : Postback takes a LONG time!