FreeTDS Development Group

[Frediano Ziglio <freddy77 AT gmail.com>]

I checked your dumps. It's not that easy to see but a SQLFreeStmt is
issued before reading all rows causing server to stop so it does not
return prepared statement id (and I hope should not keep a statement
allocated into server). This cause the handle 0 problem (with not
leak). The issue is that FreeTDS should not unprepare a not prepared
statement...

freddy77

2011/3/12 Dylan Kucera <djkucera AT sympatico.ca>:
> Hello FreeTDS enthusiasts,
>
> I recently started using FreeTDS (freetds-0.83.dev.20110306) as an
> ODBC driver for Oracle Heterogeneous Service (11.1) to be able to
> communicate from an Oracle Database Link to a SQL Server 2005
> instance.  I've run into a concerning problem that shows up when
> FreeTDS is configured to run with TDS 8.0 but not when configured to
> run 7.0.  I'm worried that the problem might show up anyway in some
> other situation even with protocol version 7.0.
>
> Aside from configuring the Oracle Heterogeneous Services links, the
> use case that causes a problem is rather simple:  Attempt to compile
> this small test procedure on the Oracle side:
>
> create or replace procedure admin.Test_FreeTDS is
>
> tOwner VARCHAR2(256);
>
> begin
>
>       SELECT "name"
>       INTO tOwner
>       FROM sys.all_parameters@rms_simulation;
>
> end Test_FreeTDS;
>
> Using TDS 8.0, it errors out, TDS 7.0 it compiles.
>
> I have created TDS Dump traces for both situations, and archived them
> in a RAR that I have broken into 3 pieces under 75K each.  Since I'm
> not sure if the mailing list limit is one 75K attachment per e-mail or
> per attachment, I'll play it safe and upload 3 different e-mails.  So
> as to reduce the size of these monstrous trace files, I removed the
> middle part of the lengthy sections that repeat many times:
>
> token.c:2300:tds_process_row(): reading column 2
> token.c:2045:tds_get_data: type 56, varint size 0
> token.c:2106:tds_get_data(): wire column size is 4
> ...repeat many times...
>
> Note that I did not remove the entire segment in any case, and
> everything that was removed was replaced with the text [Chunk
> removed].
>
> From what I can tell, the problem appears to be that FreeTDS is
> routinely calling "sp_unprepare 0" when configured to run with TDS
> protocol version 8.0, and 0 is not a valid statement handle,
> and so the error "[FreeTDS][SQL Server]Could not find prepared
> statement with handle 0." is being raised.  I briefly thought about
> creating a hack to quietly move along if an attempt to close handle 0
> was made, but then I quickly realized that this would likely lead to
> other problems including handle leaks, memory leaks... etc.
>
> Because I'm making a call to go ahead into a production setting with
> version 7.0 of the protocol configured, I'm hoping someone can provide
> me some comfort that the 7.0 trace file is showing a healthy process.
> What would be an extra bonus would be taking a look at the version 8.0
> trace file to identify what is causing the failure and letting me know
> if it can be fixed.
>
> Thank you for the driver, reading my e-mail, and for your assistance!
> Dylan.
>
> _______________________________________________
> FreeTDS mailing list
> FreeTDS AT lists.ibiblio.org
> http://lists.ibiblio.org/mailman/listinfo/freetds
>