Development | Starting Out

Performance Grid
Written by Pete Vickers  [author's bio]  [read 46083 times]
Edited by Derek

         

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This article was inspired by a recent project, Pocket RDA. Pocket RDA provides remote data access from the Pocket PC to any ADO compliant database. The results were returned into a grid control, and could be saved or copied to the clipboard.

In 'program' testing, things looked great (don't they always!!), the 30 or so customer records returned quickly. (As we all know, most 'programmer testing' is carried out with the same 10 records.) I was a bit more concerned with the performance of 100 plus records, but decided it was probably network load (software guys blame the hardware - hardware guys blame the software!).

Then when I got into 'real' testing with 2000 records plus, it crawled to a standstill.

I was using a progress bar, but it was too 'wide' to show exactly what was going on, so I decided to add a display of a record counter to the program. For the first 100 records or so, the counter 'turned' so quickly you could not see it, but then it started to really slow down, turning at approx 1 record per second. The grid was invisible to start with, and just made visible at the end of the run. It looked like the more records I added to the grid, the slower it got. This led me to do some experimentation with the grid control, and the following represents my conclusions.

This subject has been discussed on the forums several times, and several ways to speed up the display have been suggested:

1) Make the grid visible false, fill it and then visible true. I was already doing this, so not an option.

2) 'Page' the control, e.g. show 20 records. When the user scrolled down, use the scroll event in conjunction with the toprow value to go to the database for more records, i.e.

Private Sub grdRes_Scroll()
If grdRes.TopRow + 8 >= grdRes.Rows Then
If Not End_Of_File Then
grdRes.Visible = False
WaitCursor True
Get_Next_Records
End If
End If
End Sub

This worked, but I was not happy with the results.

3) Use a different control, i.e. a text box or a listview control. Maybe, but they could be as slow, and were not exactly what I wanted, as I wanted the user to be able to select a column from the grid, and this would be impossible in a text box or a listview (or would it?). I was also happy with a grid, as users are used to data being presented that way.

Rather than mess with my code, I did what all developers do, and with apologies to Walt, wrote a 'Micky Mouse' to test my theories.

The idea was to have a grid control, a text box and a listview, set up a loop to add 1000 lines of 5 items in each, and then decide what to do next. The form below shows the controls, and also a listbox, to display the results of the timing.

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