[yunqa.de] Re: Progress bar for vacuum, integrity check.
- From: Delphi Inspiration <delphi@xxxxxxxx>
- To: yunqa@xxxxxxxxxxxxx
- Date: Mon, 08 Dec 2008 12:52:42 +0100
Clyde England wrote:
>I am currently using DiSqlite3 with the object layer (TDISQLite3Database and
>TDISQLite3Statement ) and not the API directly.
>
>I have a few reasonable sized databases that I like to vacuum and or check the
>integrity from time to time.
>
>Both these operations can take a long time with large databases and there is
>no visual clue of progress. What I want to do is provide a progress bar so I
>can visually see how things are going.
>
>I suspect it requires interfacing with a callback function of some sort, but I
>am having trouble coming to grips with this and how to implement.
>
>Is this possible? Example?
sqlite3_progress_handler() is available to set up a progress handler which will
be called periodically while SQLite is busy. It works fine for VACUUM but is
surprisingly not invoked when doing the integrity check. I have created an
SQLite ticked asking to fix this.
Anyway, here is some example Delphi code for an incremental progress bar to
indicate that the database is currently busy:
//------------------------------------------------------------------------------
function TfrmMain.VacuumDatabase(
const AFileName: UnicodeString): UnicodeString;
var
Database: TDISQLite3Database;
begin
ProgressBar.Position := 0;
Database := TDISQLite3Database.Create(nil);
try
Database.DatabaseName := AFileName;
Database.Connected := True;
sqlite3_progress_handler(
Database.Handle, $400, DbProgressFunc, Self);
Database.Execute('vacuum');
finally
Database.Free;
end;
end;
//------------------------------------------------------------------------------
function DbProgressFunc(UserData: Pointer): Integer;
begin
TfrmMain(UserData).DoProgress;
Result := 0;
end;
//------------------------------------------------------------------------------
procedure TfrmMain.DoProgress;
var
i: Integer;
begin
i := ProgressBar.Position;
Inc(i);
if i > ProgressBar.Max then
i := ProgressBar.Min;
ProgressBar.Position := i;
Application.ProcessMessages;
end;
//------------------------------------------------------------------------------
Ralf
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