Open TDAMemDataTable Async

Data Abstract
1

Hello,

I’d be grateful if you could provide me with an example on how to open a TDAMemDataTable(Delphi) async. I am trying to make sure that the gui does not freeze while awaiting data from the server. Unless I’m mistaken but I think DA for XCode has methods like DARemoteDataAdapter.beginGetDataTable which I presume accomplish precisely that. Can this be mimicked DA in Delphi? . Pointers on how to achieve this will be greatly appreciated

Regards

2

Hello,

  1. You can open data tables in a separate thread.
  2. DA provides async services. You can find them in DataAbstract4_Async.pas file.
    But you can’t assign async service with RemoteDataAdapter, so you should control by
    IDataAbstractService_Async methods manually to work with data.
var
  fService: IDataAbstractService_Async;
  fData: Binary;
  aTableList: StringArray;
  aTableRequestInfoArray: TableRequestInfoArray;
begin
  aTableList := StringArray.Create;
  aTableRequestInfoArray := TableRequestInfoArray.Create;
  try
    with aTableRequestInfoArray.Add do
    begin
      IncludeSchema := True;
      MaxRecords := -1;
    end;
    aTableList.Add('CUSTOMER');
    fService := CoDataAbstractService_Async.Create(ClientDataModule.Message,
      ClientDataModule.ClientChannel);
    fService.Invoke_GetData(aTableList, aTableRequestInfoArray);
    
    repeat until fService.AnswerReceived; // wait

    fData := fService.Retrieve_GetData();
    try
      DataStreamer.ReadDataset(fData, DAMemDataTable1, True);
    finally
      FreeAndNil(fData);
    end;
  finally
    FreeAndNil(aTableList);
    FreeAndNil(aTableRequestInfoArray);
  end;
end;
1 Like
3

Thank you very much for your help. Should I go with option 1. which components must be created in that separate thread. I mean the ones that are not thread-safe.
1.Channel ?
2.Message ?
3.RDA ?

4

Hello,
Yes, you should put all these components to separate thread. Also you should put datastreamer.

5

Hello,

are there any plans to implement functions like fillAsync, applyUpdatesAsync into TDARemoteDataAdapter (which seems to be implemented in RemoteDataAdapter for Java)?

For now I think I’ll go with a seperated thread, too but there’s one open point for me:

how can I pass over a Session (created in Main-Thread) to the worker-thread? Is it just as simple as passing by the ClientID to the Channel of the thread? Or should I clone the channel (or all channel, message, rda, datastreamer) of the main thread while creating the thread?

Another option whould be the *Async-Interface, but there’s so much stuff implemented within RDA that all has to be redone in this context and for me this can’t be an option.

Best regards,
Peter

6

I’ve tried a little bit but the progress of all is not very convincing:

  1. I can just use a ClientID, assign it to any Channel and heist the session (even on a completely different computer!)
  2. There seems to be some race-conditions when doing:
    {PROBLEM:}
    stcpThread  := TROSuperTCPChannel.Create( nil );
    stcpThread.Assign( stcpMain );
    stcpThread.ClientID := stcpMain.ClientID; {Server sometimes not recognize this change}
    ``
    {WORKING:}
    stcpThread  := TROSuperTCPChannel.Create( nil );
    stcpThread.ClientID := stcpMain.ClientID;
    stcpThread.Assign( stcpMain ); {Here the channel already has the ClientID before connecting!}
    I’m not sure why a new ClientID is created anyhow (because I assumed .Assign will just clone this kind of data)
  3. Events: In the moment I disconnect this ‘cloned’ connection I will no longer be able to receive events.

So either I use a seperate thread, keep the comfort of RemoteDataAdapter and run into troubles using events or I use *Async-Interface and I’ll run into lots of problems with M/D, AutoInc, Refresh and so on because of missing Async-RDA-Implementation

Is there any way out?

Best regards,
Peter