Autocomplete in text field with large amount of items

[fr.luca]

Hello,
I'm writing a form for anagraphical data entry, and I would like city of birth & residence fields to autocomplete. The list of items to deal with is quite large, i.e. the 8000 cities of my country (Italy).
Firstly I tried to work it out using a combobox, populated at runtime with the query result from a proper db (see hereunder the code).
In order to make the application as portable as it may, and having to deal with both Windows and Linux clients, I had to notice a very different performance, in terms of time response, between the two environments, on machines with similar capabilities.
On Windows, the population of the item list took about 2 seconds, which is a long but reasonable time for my need; on Linux, the duration of the same operation increases 10 times, forcing OS to send a signal about task not responding.
Actually, it's not necessary for me to use a combobox, which control I choose only because of native autocomplete feature.
Any suggestions? Thank you.

  if openDB('codfisc.db')
  then
  begin
     combo.Clear;
     try
       dbquery.SQL.Text:= 'SELECT DESCR FROM COMUNI ORDER BY DESCR';
       dbquery.Open;
       while not dbquery.EOF do
       begin
         combo.Items.Add(dbquery.FieldByName('DESCR').AsString);
         dbquery.Next;
       end;
     finally
        closeDB;
     end;
  end;

[paweld]

Use BeginUpdate - should significantly speed up the addition of data to the ComboBox. eg.

Code: Pascal  [Select][+][-]

1. if openDB('codfisc.db') then
2.   begin
3.     combo.Items.BeginUpdate;
4.     combo.Clear;
5.     try
6.       dbquery.SQL.Text := 'SELECT DESCR FROM COMUNI ORDER BY DESCR';
7.       dbquery.Open;
8.       while not dbquery.EOF do
9.       begin
10.         combo.Items.Add(dbquery.FieldByName('DESCR').AsString);
11.         dbquery.Next;
12.       end;
13.     finally
14.       closeDB;
15.     end;
16.     combo.Items.EndUpdate;
17.   end;  
18.  

[fr.luca]

Thank you for the hint!
unfortunately, on linux time response remains the same order.
Perhaps  the combobox are not intended to work with similar amount of data, maybe I should have to seek for some external tool...

[dseligo]

Thank you for the hint!
unfortunately, on linux time response remains the same order.
Perhaps  the combobox are not intended to work with similar amount of data, maybe I should have to seek for some external tool...

Try to put data in TStringList instead of combobox, just for test. Maybe the problem is in database and not in combobox.

[fr.luca]

So, I followed your suggestion: a stringlist is now filled up when the form is created, then combo picks it up at showtime.
The form takes some time before appearing, but that's ok.
By the way,  I tried to use a text file instead of  the former sqlite db, to store the list to be retrieved. Nothing significant occurred.
I suppose there should be some kind of tuning in file accessing and management, but I know nothing about the matter.
Anyway, thank you a lot, now it works decently!