Refresh to DBGrid and cursor points to the same record.

[mlara]

Hi!

I have an important question. I do a query to a Firebird database. I use the MDO (Mercury Database Objects) components for access the database. When I do click over the title of each column, I change the clause 'ORDER BY' and re-open the query. Then I execute the method 'Locate' to position the cursor. The problem is that when I execute this method, the component (TMDOQuery) scroll by all records so far the record searched. This operation takes several seconds (sometimes a lot of seconds). I don't want use the component TClientDataSet. The objetive is finds a solution as it does the IBExpert program. This program order the results and manteins the cursor on the same location.

How can I do it?

Maybe the problem is in use the method 'Locate', but I too want search records in a dbgrid. When the grid has a lot of records (more than 1000), the quest causing a lot of 'Fetch Next', and takes a lot of time.

I must solve this problem, using forced a dbgrid.

 

[DjangMan]

Use a bookmark:

var
  Bookmark:TBookmark;

  YourTable.DisableControls;
  try
    Bookmark := YourTable.GetBookmark;

    <do some processing here>

    YourTable.GotoBookmark(Bookmark);
  finally
    YourTable.EnableControls;
    YourTable.FreeBookmark(Bookmark);
  end;

 

[mlara]

No, the use of Bookmarks is not appropriate. A bookmark contains a position of record. When I change the clause 'ORDER BY' and re-open the query, the records changes the order, and the bookmark brings me to another record.

 

[DjangMan]

If the locate will cause scrolling then you'll need to use the disable/enable controls methods to at least prevent the grid from expending all the effort of drawing the records moving past.

 

[mlara]

Of course, I execute the method DisableControls, then the control dbgrid don't show the records while but do it (All the 'Fetch next' neccesary). Then the problem consists in these:

When I execute the method 'Locate' the control (TMDOQuery based in TIBQuery) scroll by all records do it one by one. This procedure take a lot of time and no is appropriate. For best explai, the code is:

procedure TForm.DBGridTitleClick(Column: TColumn);
var
ColumnName: string;
CodigoInt: Integer;
begin
// Current record
CodigoInt := Query.FieldByName('CodigoInt').AsInteger;

// Change the clause 'ORDER BY'
Query.SQL[Query.SQL.Count-1] := 'ORDER BY ' + ColumnName;

// Re-Open the query
Query.DisableControls;
Actualizar(CodigoInt); // another procedure
Query.EnableControls;
end;

procedure TForm.Actualizar(CodigoInt: Integer);
begin
// Open
Query.Open;

// Current record
if CodigoInt <> -1 then
Query.Locate('CodigoInt', CodigoInt, []); // Here is the problem.
end;


Thanks for your comments.