[Iodbc-bugs] Problem with SQLCancel() in iODBC

[Bogdan D. <bog...@or...>]

Hi,

I found a problem with SQLCancel() function in iODBC.

Normally SQLCancel() is called upon an active statement from a separate 
client app thread to break the execution of a long running statement. 
However, the current implementation (3.52.8) of SQLCancel() does not 
allow that.

Here is the fragment from hstmt.c (lines 1135-1145):

SQLRETURN SQL_API
SQLCancel (SQLHSTMT hstmt)
{
   ENTER_STMT (hstmt,
     trace_SQLCancel (TRACE_ENTER, hstmt));

   retcode = SQLCancel_Internal (hstmt);

   LEAVE_STMT (hstmt,
     trace_SQLCancel (TRACE_LEAVE, hstmt));
}

The ENTER_STMT macro checks for stmt_cip (if the call is in progress for 
this handle) and returns the error [S1010] "Function sequence error".

For instance, MySQL ODBC driver does not use the same particular hstmt. 
It only gets the connection ID and opens a new connection (SQLHDBC) and 
a new statement (SQLHSTMT) handles to kill the running query.

There are a few ways to deal with the problem, but I think that the 
easiest one would be introducing another macro like ENTER_STMT_ASYNC, 
which would take into account the asynchronous nature of SQLCancel() calls.

Please let me know if you have any questions.
Thanks.

-- 
Best Regards,
Bogdan Degtyariov
Senior Developer
MySQL/Sun/Oracle
Melbourne, Australia