[freetds] Pending result limitation

Sebastien FLAESCH sf at 4js.com
Tue Jun 23 09:40:22 EDT 2009


First, thanks a lot for all the work you do Frediano...

I believe that FAQ topic should mention that the unique-statement
limitation is related to the TDS protocol/library only... right?

There is in fact no concurrent SQL statement limitation when using
server-side cursors with ODBC... correct?

Seb

Frediano Ziglio wrote:
> 2009/6/23 Sebastien FLAESCH <sf at 4js.com>
>> Hi all,
>> (I am using ODBC)
>>
>> The FAQ talks about an annoying limitation:
>>
>> "Why does each connection support only one query at a time?"
>>
>> http://www.freetds.org/faq.html#pending
>>
>> I believe this is no longer true... can someone confirm?
>>
>> I guess this is related to a TDS protocol version... right?
>>
>> Thanks!
>> Seb
> 
> It should be possible to overcome this limitation using MARS which is
> currently not supported by FreeTDS. As said many time you can also
> overcome this limit using cursors. There is no planning for protocol
> 7.2 (mssql 2005 which supports MARS) but currently I have patches for
> SQL_VARIANT and MSXML on my quilt directory. I think that one of the
> greatest limit of protocol 7.2 is the way BLOBs are handled. Even if
> you use TEXT/NTEXT/IMAGE and even if TEXTPTR function returns a proper
> value it seems that server doesn't send textptr with data type (it
> replace with dummy data). This is not a problem for ODBC but is a big
> problem for dblib (and perhaps for CTlib) where writetext require to
> know textptr. As usual patches, tests, man work and suggestions are
> always welcome.
> 
> Currently I'm working on:
> - UNICHAR on ctlib
> - empty string on ctlib
> - numeric on dblib
> - client charset on freebcp
> That is too much to add MARS :)
> 
> Regards
>   Frediano Ziglio
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