How Transactions work

BIZ TMS Aurelius
1

Hi,
  We are facing some data inconsistency, when we have object(table) inhereted from another object(table), like TMember = class(TCustomer).
  How transactions work on aurelius? i don't find it one documentation.
thanks

2

Use it like this:

var
  Trans: IDBTransaction;
begin
  Trans := Manager.Connection.BeginTransaction;
  try
    //...
    Trans.Commit;
  expect
    Trans.Rollback;
    raise;
  end;
end;
3

Ok,
 Manager.Flush;
By default aurelius Start transaction and commit/rollback with "Manager.Flush"?
we have always, start transaction? and in this particular case (inheritance)?

thanks Wagner

4

Yes, you have to create transactions.

5

Hi,
  try
    Trans := Manager.Connection.BeginTransaction;
    Manager.Flush;
    Trans.Commit;
  except  on E : EFDDBEngineException do
  begin
     Trans.Rollback;
  end;

Is this correct? Why Trans.Rollback doesn't really Rollback?
Tanks, Wagner

6

Yes, the code seems correct, you could just raise the exception after the rollback in case you want the error to be propagated.

7

Hi, Wagner
    I try again, and can't make transactions work. here is the code:


  TUserGrp = class
  private
    [Column('Id', [TColumnProp.Required])]
    FId: Int64;

    [Column('Description', [TColumnProp.Required], 20)]
    FDescription: string;
  public
    property Id: Int64 read FId write FId;
    property Description: string read FDescription write FDescription;
  end;


  TUserX = class
  private
    [Column('Id', [TColumnProp.Required])]
    FId: Int64;

    [Column('UserName', [TColumnProp.Required], 20)]
    FUserName: string;

    [Column('RecVersion', [TColumnProp.Required])]
    FRecVersion: TDateTime;

    [Association([TAssociationProp.Lazy, TAssociationProp.Required], CascadeTypeAll - [TCascadeType.Remove])]
    [JoinColumn('UserGrpId', [TColumnProp.Required], 'Id')]
    FUserGrpId: Proxy<TUserGrp>;    

    function GetUserGrpId: TUserGrp;
    procedure SetUserGrpId(const Value: TUserGrp);
  public
    property Id: Int64 read FId write FId;
    property UserName: string read FUserName write FUserName;
    property UserGrpId: TUserGrp read GetUserGrpId write SetUserGrpId;
  end;


procedure TDBUserX.SaveUpdateT(NewDBObject: TUserX; const pSysResponse: TSysResponse);
var DBObject: TUserX;
  Trans: IDBTransaction;
begin
  if NewDBObject.Id = 0 then     //INSERT
  begin
    pSysResponse.Done := pInserted;
  end
  else                          //UPDATE
  begin
    pSysResponse.Done := pUpdated;
    DBObject := Manager.Find<TUserX>(NewDBObject.Id) as TUserX;// just to Check Record Version
    if DBObject <> nil then
      CheckRecVersion(NewDBObject.RecVersion, DBObject.recVersion, NewDBObject.Id, pSysResponse )
      //Validate Data DBObject vs NewObject
    else
      NotFound(NewDBObject, NewDBObject.Id, pSysResponse);
  end;

  if pSysResponse.Success then
  begin
    NewDBObject.RecVersion := now;
    NewDBObject := Manager.Merge(NewDBObject);
    Trans := Manager.Connection.BeginTransaction;
    try
      Manager.Flush;
      Trans.Commit;
    except
    on E : EFDDBEngineException do
    begin
      Trans.Rollback;
      raise;
    end;
  end;
  end;
end;

if you try, "SaveUpdateT" with UserGrp.Description:= nil, "Manager.Merge" raise an exception, Trans.Rollback is executed,
but a record is inserted in Tuser!!!

8

Do the merge after the transaction starts, if the object has no id, merge will save (insert) it.

9

Ok, works fine, but to save objects to database, should use "Manager.Merge" or ""Manager.Flush" or both?

10

Both