BDE vs ADO in Delphi

Question

Please note the Edit below for a lot more information, and a possible solution

We recently modified a large Delphi application to use ADO connection

Answer 1

i found the performance problems with ADOExpress years ago:

• ADO vs ADOExpress time trials. Not good for ADOExpress (6/7/2005)
• ADO vs ADO Express Time Trials (redux) (12/30/2007)

Note: Before ADO became a standard part of Delphi, Borland was selling it as an addon called ADOExpress. It was simply object wrappers around Microsoft's ActiveX Data Objects (ADO) COM objects.

i had tested three scenarios

• using ADO directly (i.e. Microsoft's COM objects directly)
• using ADOExpress (Borland's object wrappers around ADO)
• specifying .DisableControls on the TADOQuery before calling Open

i discovered

• use Query.DisableControls to make each call .Next 50x faster
• use Query.Recordset.Fields.Items['columnName'].Value rather than Query.FieldByName('columnName') to make each value lookup 2.7x faster

• using TADODataSet (verses TADOQuery) makes no difference

                                  Loop Results        Get Values 
  ADOExpress:                         28.0s              46.6s 
  ADOExpress w/DisableControls:        0.5s              17.0s 
  ADO (direct use of interfaces):      0.2s               4.7s 
  

Note: These values are for looping 20,881 rows, and looking up the values of 21 columns.

Baseline Bad Code:

var
   qry: TADOQuery;
begin
   qry := TADOQuery.Create(nil);
   try
      qry.SQL.Add(CommandText);
      qry.Open;
      while not qry.EOF do
      begin
         ...
         qry.Next;
      end;

Use DisableControls to make looping 5000% faster:

var
   qry: TADOQuery;
begin
   qry := TADOQuery.Create(nil);
   try 
      qry.DisableControls;
      qry.SQL.Add(CommandText);
      qry.Open;
      while not qry.EOF do
      begin
         ...
         qry.Next;
      end;

Use Fields collection to make value lookups 270% faster:

var
   qry: TADOQuery;
begin
   qry := TADOQuery.Create(nil);
   try 
      qry.DisableControls;
      qry.SQL.Add(CommandText);
      qry.Open;
      while not qry.EOF do
      begin
         value1 := VarAsString(qry.Recordset.Fields['FieldOne'].Value);
         value2 := VarAsInt(qry.Recordset.Fields['FieldTwo'].Value);
         value3 := VarAsInt64(qry.Recordset.Fields['FieldTwo'].Value);
         value4 := VarAsFloat(qry.Recordset.Fields['FieldThree'].Value);
         value5 := VarAsWideString(qry.Recordset.Fields['FieldFour'].Value);
         ...
         value56 := VarAsMoney(qry.Recordset.Fields['FieldFive'].Value);
         qry.Next;
      end;

---

Since it is a common enough problem, we created a helper method to solve the issue:

class function TADOHelper.Execute(const Connection: TADOConnection; 
       const CommandText: WideString): TADOQuery;
var
   rs: _Recordset;
   query: TADOQuery;
   nRecords: OleVariant;
begin
   Query := TADOQuery.Create(nil);
   Query.DisableControls; //speeds up Query.Next by a magnitude
   Query.Connection := Connection;
   Query.SQL.Text := CommandText;
   try
      Query.Open();
   except
      on E:Exception do
      begin
         Query.Free;
         raise;
      end;
   end;
   Result := Query;
end;