FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: ZIGLIO, Frediano, VF-IT
> Sent: Friday, April 08, 2005 3:21 AM
> 
> Well, if you read my mail you will discover 4 bugs:
> - 1 MS odbc driver
> - 2 FreeTDS
> - 1 DBD::ODBC

I didn't quite understand your analysis.  I think I do now.  

> However the issue came from DBD::ODBC that do not handle
> SQLMoreResults if it returns SQL_ERROR. It works on MS odbc
> driver only because MS odbc driver discard error... I'm updating
> raiserror.c test to catch this case (and do some fix)

Two choices: make FreeTDS emulate Microsoft's driver, or make DBD::ODBC
do the right thing.  I think #2 is better, if only because being
bug-compatible is hard: Sybase's driver will have different bugs.  

It would be cool to add FreeTDS to the (short) list of "known
compatible" drivers.  From .cpan/build/DBD-ODBC-1.13/README:

KNOWN COMPATIBLE Drivers (w/level 2 calls):
Driver                     Version     Platform 
Microsoft SQL Server       v 2.65.0240 NT 4.0
Intersolv Oracle7 Driver*  v 3.00.0000 NT 4.0

We could be #3!  ;-)  

It looks like the code in .cpan/build/DBD-ODBC-1.13/dbdimp.c::imp_sth_t
(line 2195 or so) is where SQLMoreResults is handled.  I wouldn't mind
trying to patch it, but I have to understand the problem better.  AIUI,
SQLMoreResults may return SQL_SUCCESS_WITH_INFO or SQL_ERROR, depending
on the severity argument to RAISERROR.  

My test used severity 16.  I tried severity 9.  Get this: when I use
severity 9 AND I install an error handler ($dbh->{odbc_err_handler} =
\&err_handler;)), THEN odbc_rpc.pl prints the message: (!)

Executing: "{? = call t }" with parameters ''
execute returned: '-1'
Result #1:
[FirstResult]
'Here is the first row'
===> state:  msg: This is an example error message.
Result #2:
[LastResult]
'Here is the last row'

This using 0.63.  0.62.3 still ignores the message.  

More data
---------

I called the same test procedure, using severities 9 and 16, using
ActiveState Perl on a Windows box (using Microsoft's driver).  The
result: severity 9 was not printed, and 16 led to a sequence error. It
did not matter whether odbc_err_handler was installed or not.  

Microsoft, Severity 9:
$ perl odbc_rpc.pl  [...] t
odbc_async_exec is: 1
Binding parameter #1, the return code

Executing: "{? = call t }" with parameters ''
execute returned: '-1'
Result #1:
[FirstResult]
'Here is the first row'
Result #2:
[LastResult]
'Here is the last row'

No message.  

Microsoft, Severity 16:
$ perl odbc_rpc.pl  [...] t
odbc_async_exec is: 1
Binding parameter #1, the return code

Executing: "{? = call t }" with parameters ''
execute returned: '-1'
Result #1:
[FirstResult]
'Here is the first row'
===> state: 42000 msg: This is an example error message.
            ^^^^^ not set by RAISERROR
DBD::ODBC::st fetchrow failed: (DBD: st_fetch/SQLMoreResults err=-1) at
odbc_rpc.pl line 98.
'Here is the first row' <== First row again!
===> state: HY010 msg: Function sequence error
DBD::ODBC::st fetchrow failed: (DBD: st_fetch/SQLFetch err=-1) at
odbc_rpc.pl line 98.

It looks like $sth->fetchrow returned the first row twice.  

Conclusions
-----------

1.  0.63 + odbc_err_handler + (severity < 11) is OK
2.  odbc_err_handler requires odbc_async_exec.  One of these affects
DBD::ODBC's ability to recognize RAISERROR messages.  
3.  DBD::ODBC does not cope with higher severities.  

Calling all Perlheads!  Is the fetch loop in odbc_rpc.pl right and good?
Should it be doing something else?  If the test is valid, it looks like
it's time to send a problem report to dbi-users AT perl.org.  

--jkl




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