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OnFilterRecord and DBGrid?

Posted on 2002-06-12
Medium Priority
Last Modified: 2010-04-04
Hello, Everyone.

Im using the OnFilterRecord Event on a Paradox Table. Has anyone noticed even though if Filtered=false for the Table, the DBGrid scrolls slower? If I take off the OnFilterRecod event from code,it will go back to normal fast scrolling speed.

Its just weird, when Filtered is set to false it deosn't even goto any line in that event. So why does it become slow? The scrolling is even faster when Filter=true.

So go should be the other way around. Filtering should make things slower ;-)

Any suggestions are very welcome.

Thanks very much.

Im using a Table with about 30,000 records.And a Intel P3 1gz, with 256mb ram , and gb's of free disk space. The key is using a very large Table.

If you would like to test , try using a very large
Table . Set the Filtered property to false during design time, and add some commented lines to the OnFilterRecord Event(no real code is needed there , its just to make the event exist) . Now compile and run , you should have the same results.


Question by:superpower
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LVL 27

Expert Comment

ID: 7074742
? weird ... listening

Expert Comment

ID: 7074748
Try this to avoid evaluation

Table1.OnFilterRecord := nil;

Best Regards.

Author Comment

ID: 7076123

No , I never get to this situation.

Table1.OnFilterRecord := nil;

Any other ideas?

BTW, it isnt as slow if I use a smaller Table. If you would like to test , try using a fairly large Table (more than 1000 records at least), set the Filtered property to false during design time, and only add code the OnFilterRecord Event . Now compile and run , you should have the same results.

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LVL 27

Expert Comment

ID: 7076163
>you should have the same results
no, i have no difference (maybe my workstation is too fast)

Author Comment

ID: 7076167

On the other hand, for tests try to use a Table with close enough records to 30,000 just as Im testing with :-)

If you dont have one, you experts know how to make one through a loop .
LVL 44

Expert Comment

ID: 7077373
Well I just tested with 30,000 records with and without an OnFilterRecord on a Paradox table and there appeared to be no difference in the srolling speed.

PII 450 384MB's RAM Win2000

The Crazy One

Author Comment

ID: 7078966

Here is the code I used,just to better illustrate.

unit cfilter;
   {Delphi3 Pro, also tried D5}

 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
 Grids, DBGrids, Db, DBTables;

 TForm1 = class(TForm)
   Table1: TTable;

{40,000 record table(about 30field Table), Filtered Property is set to false , and Active is set to true during design time}

{same table structure with 8,000 records isnt so harshly

   DataSource1: TDataSource;
   DBGrid1: TDBGrid;
   procedure Table1FilterRecord(DataSet: TDataSet; var Accept: Boolean);
   { Private declarations }
   { Public declarations }

 Form1: TForm1;


{$R *.DFM}

procedure TForm1.Table1FilterRecord(DataSet: TDataSet;
 var Accept: Boolean);

{testing lines}
{take comments out and watch how fast the scrolling speed becomes}



Author Comment

ID: 7079457

Problem solved by myself just before I ran out of hope. This was one that really got me stuck.

I found a work around to this bug(It maybe so, or not) , becuase of all the code samples for OnFilterRecord in books, websites that Ive looked at ,had no such mention to do this.

On the OnShow event of the Form I just use


It seems Delphi doesn't like that event to be linked , when Filtered=false and some code exists in that event. So I unlink it. And call it back when I want the filtering to start.

Table1.OnFilterRecord := Table1FilterRecord;

But this was a rather tricky one. Becuase anyone trying the code on even a 10,000 record Table wouldnt even seen any difference. It had to be a 30k or 40k record Table with 30fields , in my case.

So do I get those points :-)
LVL 27

Expert Comment

ID: 7079466
really curious, because i could not reproduce

glad you had it solved yourself

ask at community-support for keep this q
into paq and refunds your points

meikl ;-)

Author Comment

ID: 7094392
Thank everyon for trying to help anyway. Still appreciated.


But I have one question coming up that maybe you can answer. :-) So il recycle these pionts I get back.

Accepted Solution

Moondancer earned 0 total points
ID: 7094569
Thanks all.  200 points refunded, item moved to our PAQ at zero points and closed.
Moondancer - EE Moderator

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