Occasionally getting "error reading data from the connection"

rbuser

Hi,

when previewing reports the error "error reading data from the
connection" is displayed occasionally. We have ReportBuilder 15.04 and
the underlying database is Firebird.
The first question I'd like to ask is what are the possible causes of this?

I have read (e.g. here
https://groups.yahoo.com/neo/groups/firebird-support/conversations/topics/15921)
that this error might be because of multiple threads using the same
database connection. Furthermore, in a post on this newsgroup dated
9.5.2012, it's stated that: "The new RB 14 viewer generates all pages in
a background thread for efficient execution. This is necessary due to
the fact that unlike RB 12, multiple pages must be requested at the same
time. For RB 12, only a single page needed to be requested.
You can revert back to the RB 12 style viewer by setting the
PreviewFromSettings.SinglePageOnly property to True."

I'd like to set "Report.PreviewFromSettings.SinglePageOnly := True;" for
all existing reports to see if that helps. Is there any easy way to
accomplish that without modifying every single report (i.e. perform this
modification centrally in one place)? I have tried to do this in the
BeforePreview event as in this example:
http://www.digital-metaphors.com:8080/Plugins/Dialogs/Preview_Plugin,
but that recursively calls TppPrintPreview.Init until a stack overflow
is returned.

Any other suggestions about how to solve this error are also welcome.

Thanks in advance for any answers,
Jure

nicocizik

Hi Jure,

Setting the Report.PreviewFormSettings in the BeforePreview will cause
an infinite loop due to the fact that the preview is automatically
updated when a property is set.

You will want to set the Viewer.SinglePageOnly property to True inside
the BeforePreview. This however still leaves the issue of the
Multi-Page View buttons still showing. You will also need to manually
hide them. This is not ideal, I will look at rearranging this code so
it can be more elegantly done.

procedure TMyPreviewPlugin.BeforePreview;
begin
inherited;

//Force SinglePageOnly
Viewer.SinglePageOnly := True;

//Hide un-needed buttons
SinglePageButton.Visible := not(Viewer.SinglePageOnly);
TwoUpButton.Visible := not(Viewer.SinglePageOnly);
ContinuousButton.Visible := not(Viewer.SinglePageOnly);
ContinuousTwoUpButton.Visible := not(Viewer.SinglePageOnly);

end;

nardmoseley

Hi Jure,

Here are a couple of solutions:

1. If loading templates from file/database use Report.Template.OnLoadEnd to
set report properties.

or

2. Implement a utility routine, such as myInitialReport(aReport: TppReport)
and then call the routine prior to calling report.Print. Or make a routine
called myPreviewReport(aReport: TppReport) that initializes the properties
and calls print.



Best regards,

-
Nard Moseley
Digital Metaphors
www.digital-metaphors.com

rbuser

Nico and Nard,

thanks to both of you for your suggestions, I've implemented the ones
Nico suggested. Hopefully it will solve the "error reading data from the
connection" error.

Thank you and regards,
Jure