Re: Return value of SQLRowCount with operations producing no result

Il giorno 13/gen/2012, alle ore 22:03, [email protected] ha scritto:

> 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().  

I don't remember why there is this if... I should check on cvs history. Have you tried unittests??

> 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);
>    

This test could be replaced by a compile test.

>    *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

Bye
  Frediano