const
  MinCount = 100000;
var
  Form1: TForm1;

implementation 
...
procedure TForm1.Button2Click(Sender: TObject);
var
  ExecSQL: TIBSQL = Nil;
  startTick: PtrInt = 0;
  endTick: PtrInt = 0;
  MyThread: TMyThread = nil;
  i: Integer;
  rNode: PVirtualNode = nil;
  rNodeData: PMyRec = nil;
begin
  for i:= 0 to Pred(StatusBar1.Panels.Count) do
    StatusBar1.Panels[i].Text:= '';

  if not IBDatabase1.Connected then IBDatabase1.Connected:= True;

  ExecSQL:= TIBSQL.Create(Self);

  try
    try
      startTick:= GetTickCount64;
      IBTransaction1.StartTransaction;

      ExecSQL.Database:= IBDatabase1;
      ExecSQL.Transaction:= IBTransaction1;

      ExecSQL.SQL.Text:= 'SELECT COUNT(ID) CNT FROM TEST';
      ExecSQL.ExecQuery;

      if (ExecSQL.FieldByName('CNT').AsInteger > MinCount) then
      begin
        MyThread:= TMyThread.Create(True);
        MyThread.Start;
      end;

      ExecSQL.SQL.Text:= 'SELECT ID, NAME FROM TEST';
      ExecSQL.ExecQuery;

      VST_partial.BeginUpdate;
      try
        VST_partial.Clear;

        while (ExecSQL.RecordCount < Succ(MinCount)) do
        begin
          rNode:= VST_partial.AddChild(nil);
          rNodeData:= VST_partial.GetNodeData(rNode);
          rNodeData^.ID:= ExecSQL.FieldByName('ID').AsInteger;
          rNodeData^.Name:= ExecSQL.FieldByName('NAME').AsString;
          VST_partial.AddChild(rNode);
          ExecSQL.Next;
        end;
      finally
        VST_partial.EndUpdate;
        VST_partial.ScrollIntoView(rNode,True);
        VST_partial.AddToSelection(rNode);
        VST_partial.Expanded[rNode]:= False;
      end;

      endTick:= GetTickCount64;

      StatusBar1.Panels[0].Text:= Format('Executing time of inserting %d records into the VST_partial is %d msec',
                                    [MinCount, (endTick - startTick)]);
      StatusBar1.Panels[0].Width:= StatusBar1.Canvas.TextWidth(StatusBar1.Panels[0].Text)
                        + StatusBar1.Canvas.TextWidth('W');
      IBTransaction1.Commit;
    except
      on E:Exception do
      begin
        IBTransaction1.Rollback;
        {$IFDEF MSWINDOWS}
        ShowMessage(WinCPToUTF8(E.Message));
        {$ELSE}
        ShowMessage(E.Message);
        {$ENDIF}
      end;
    end;
  finally
    FreeAndNil(ExecSQL);
  end;
end; 

procedure TMyThread.Execute;
begin
  try
    if not Fdbase.Connected then Fdbase.Connected:= True;

    FTrans.StartTransaction;
    FexecSQL.ExecQuery;//SQL.Text:= 'SELECT ID, NAME FROM TEST';

    Form1.VST_full.Clear;

    while not FexecSQL.Eof do
    begin
      Synchronize(@AddNodeToExtVST);
      Sleep(1);
      FexecSQL.Next;
    end;

    FTrans.Commit;
  except
    on E:Exception do
    begin
      FTrans.Rollback;
      {$IFDEF MSWINDOWS}
      ShowMessage(WinCPToUTF8(E.Message));
      {$ELSE}
      ShowMessage(E.Message);
      {$ENDIF}
    end;
  end;
end; 

procedure TMyThread.AddNodeToExtVST;
var
  aNode: PVirtualNode = nil;
  aNodeData: PMyRec = nil;
begin
  with Form1 do
  begin
    //VST_full.BeginUpdate;
    try
      aNode:= VST_full.AddChild(nil);
      aNodeData:= VST_full.GetNodeData(aNode);

      if Assigned(aNodeData) then
      begin
        aNodeData^.ID:= FexecSQL.FieldByName('ID').AsInteger;
        aNodeData^.Name:= FexecSQL.FieldByName('NAME').AsString;
        VST_full.AddChild(aNode);
      end;

    finally
      //VST_full.EndUpdate;
      //VST_full.ScrollIntoView(aNode,True);
    end;
  end;
end; 

rNodeData:= VST_partial.GetNodeData(rNode);
          rNodeData^.ID:= ExecSQL.FieldByName('ID').AsInteger;
          rNodeData^.Name:= ExecSQL.FieldByName('NAME').AsString;
          VST_partial.AddChild(rNode);

select S.ID s_id, S.NAME s_name, C.NAME c_name from STREET S
join CITY C on C.ID = S.CITY_ID

// Строка коннекта
  c_dbn = '127.0.0.1/3100:D:/Trash/tstVST/streets.fdb';
// Путь к библиотеке fbclient.dll
  c_lbn = 'D:/Program Design/Delphi2007/EstExe/bcSupport/fbClient/fbclient.dll';

select ID from STREET

fIds: array of Integer;

procedure TForm1.LoadIds;
var
  i: Integer;
begin
  qSelectIds.ExecQuery;
  SetLength(fIds, 10000);
  i := 0;
  while not qSelectIds.Eof do
  begin
    if i = Length(fIds) then
      SetLength(fIds, Length(fIds) + 10000);
    fIds[i] := qSelectIds.Fields[0].AsInteger;
    Inc(i);
    qSelectIds.Next;
  end;
  SetLength(fIds, i);
end;

  vstMain.RootNodeCount := Length(fIds);

select S.NAME, C.NAME
from STREET S
join CITY C on C.ID = S.CITY_ID
where S.ID = :ID   

procedure TForm1.vstMainGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Column: TColumnIndex; TextType: TVSTTextType; var CellText: WideString);
begin
  if not Assigned(Node) then Exit;
  if not (Column in [0, 1]) then Exit;

  if qSelectAll.Params[0].AsInteger <> fIds[Node.Index] then
  begin
    qSelectAll.Params[0].AsInteger := fIds[Node.Index];
    qSelectAll.ExecQuery;
  end;
  CellText := qSelectAll.Fields[Column].AsString;
end;