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EMySQLException #HY000Unknown thread id: 256

sean wrote: Then I cannot compile the application:
"Unit MyDacMonitor was compiled with a different version of DBAccess.TDAParams"

I upgraded from Mydac4 to Mydac 5.00.1.6 just last week.

sean wrote:As regards threads, mydac obviously uses threads, because sometimes
when I quite the application, instead of the 'MySQL gone away' message,
I get:

EMySQLException #HY000Unknown thread id: 256

The thread ID number changes.

Does this help to trace the issue?

1) Close IDE
2) Uninstall MyDAC
3) Search for MyAccess.*, DBAccess.*, mydac*.bpl, dac*.bpl etc files at your HDD and delete them
4) Remove from the project directory all files made by compiler and linker
5) Remove from the registry (HKCU\Software\Borland\Delphi\7.0\Known Packages) all the links to MyDAC packages (mydac*.bpl, dac*.bpl)
6) Run IDE and check that it is started without errors
7) Close IDE
Install MyDAC once more

This is an internal MyDAC exception, you should not see this error if you run your application without debugging. It can happen if you close your application that has unfetched datasets in FetchAll=False mode

procedure CloseMyTable(Table: TMyTable);
begin
  if (Table.State = dsInactive) then begin
    debug2('CloseMyTable, already closed: ' +Table.TableName);

  end else if (Table.State in [dsBrowse,dsSetKey]) then begin
    try
      //debug2('CloseMyTable: ' +Table.TableName);
      Table.Close;
    except
      log_error('CloseMyTable: cannot close ' +Table.TableName);
    end;
  end else if (Table.State in [dsEdit,dsInsert]) then begin
    debug2('CloseMyTable: Cancel & Close ' +Table.TableName);
    try
      Table.Cancel;
      Table.Close;
    except
      log_error('CloseMyTable: cannot cancel & close ' +Table.TableName);
    end;
  end else begin
    log_error('CloseMyTable, in unexpected state: ' +Table.TableName);
  end;
End;

sean wrote:Can I catching this somehow and cleanly close datasets, so I can at least get rid of these design time errors?

sean wrote:I wonder if its how I close tables? I use the following function to close most tables explicitly:

  try 
    Table.Close; 
  except 
  on e: Exception do 
      log_error('CloseMyTable: cannot close ' + Table.TableName 
                    + ' e.ClassName: ' + e.ClassName + ' e.Message: ' + e.Message); 
  end; 

Just call the corresponding dialog from the Tools IDE menu, and add EMySQLException to the Exception Types to Ignore on the Language Exception tab.