Re: Return value of SQLRowCount with operations producing no result

On Fri, Jan 13, 2012 at 03:09:10PM -0500, Jack Lloyd wrote:
> Hi,
> 
> I've noticed a difference in behavior in FreeTDS between 0.82 and 0.91
> when using it via iODBC 3.52.7. I'm using FreeTDS on Linux, talking to
> a SQL Server 2008 R2 instance. In 0.82, calling SQLRowCount when the
> statement was something that does not produce a result (for instance
> "set lock_timeout 1000", "create table ..." or "drop table ..."), the
> call returns SQL_SUCCESS, setting the output parameter to -1. This
> behavior matches that seen running on Windows using the Microsoft ODBC
> driver. In contrast in 0.91 (as well as the 0.92 snapshot I tried,
> dated 20120105), SQLRowCount will return SQL_ERROR and does not set
> the output parameter. GetDiagRec returns "Function sequence error".

Bug.  :-(

http://msdn.microsoft.com/en-us/library/windows/desktop/ms711835%28v=vs.85%29.aspx

The 24000 diagnostic is not a valid return code for SQLRowCount().  
HY010 (Function sequence error) is a DM error, and is not caused by the
situation you describe.  

Here is the code:

SQLRETURN
_SQLRowCount(SQLHSTMT hstmt, SQLLEN FAR * pcrow)
{
	TDSSOCKET *tds;

	ODBC_ENTER_HSTMT;

	tdsdump_log(TDS_DBG_FUNC, "_SQLRowCount(%p, %p)\n", 
			hstmt, pcrow);

	tds = stmt->dbc->tds_socket;
	if (stmt->row_status == NOT_IN_ROW) {
		odbc_errs_add(&stmt->errs, "24000", NULL);
		ODBC_EXIT_(stmt);
	}

	*pcrow = -1;
	if (stmt->row_count != TDS_NO_COUNT)
		*pcrow = stmt->row_count;
	ODBC_EXIT_(stmt);
}

Looking over the possible return codes for SQLRowCount(), I think the error
checking can be removed, yielding:

SQLRETURN
_SQLRowCount(SQLHSTMT hstmt, SQLLEN FAR * pcrow)
{
	ODBC_ENTER_HSTMT;

	tdsdump_log(TDS_DBG_FUNC, "_SQLRowCount(%p, %p)\n", hstmt, pcrow);

	assert(TDS_NO_COUNT == -1);
	
	*pcrow = stmt->row_count;

	ODBC_EXIT_(stmt);
}

Please try that.  I'll commit it if it works and no one objects.  

> SQLNumResultCols will also fail in 0.91 in this situation

The code that would do that is removed in CVS HEAD with "#if 0". 

--jkl