[freetds] Microsoft SQL Server versions and FreeTDS

Geoff Montee geoff.montee at gmail.com
Tue Apr 8 14:20:33 EDT 2014


Thanks for the insight. That clarifies a lot.

Geoff


On Tue, Apr 8, 2014 at 2:08 PM, Frediano Ziglio <freddy77 at gmail.com> wrote:

> 2014-04-08 13:39 GMT+01:00 Geoff Montee <geoff.montee at gmail.com>:
> > I wrote an open source TDS foreign data wrapper for PostgreSQL using your
> > implementation of DB-Library:
> >
> > https://github.com/GeoffMontee/tds_fdw
> >
> > I mainly wrote it to connect to Sybase databases, but its compatibility
> > with Microsoft SQL Server is a nice added benefit.
> >
> > Your TDS protocol page hasn't been updated in a while:
> >
> > http://www.freetds.org/userguide/choosingtdsprotocol.htm
> >
>
> Userguide on website refer to stable release, we are developing stuff
> for mssql 2012 (mssql 2008 R2 have very small changes in the
> protocol... mostly nothing!). Keep in mind that client and server
> decide together the protocol to use. Actually all server versions
> support protocols from 4.2 to protocol specific to the server version
> (for instance 7.2 for mssql 2005). As client you can use whatever
> protocol server provides.
>
> > It's missing MS SQL Server 2008 R2, MS SQL Server 2012, and MS SQL Server
> > 2014. I'm curious, does your implementation of DB-Library support these
> > newer versions of MS SQL Server? I ask because Microsoft's own
> > documentation says that they may drop DB-Library support in the future:
> >
> > http://technet.microsoft.com/en-us/library/aa174484%28v=SQL.80%29.aspx
> >
> > "While the DB-Library API is still supported in Microsoft SQL Server
> 2000,
> > no future versions of SQL Server will include the files needed to do
> > programming work on applications that use this API. Connections from
> > existing applications written using DB-Library will still be supported in
> > the next version of SQL Server, but this support will also be dropped in
> a
> > future release. When writing new applications, avoid using DB-Library.
> When
> > modifying existing applications, you are strongly encouraged to remove
> > dependencies on DB-Library."
> >
>
> The reason is that Microsoft db-library only support protocol 4.2 (the
> protocol introduced by... I think Sybase 4.2 before ms acquired
> licences and forked the code! I never worked on such releases, for me
> mssql starts with 7.0). Our db-library support newer versions, current
> development up to 7.3. Well... in 7.3 (but not on 7.2) MS removed some
> information (the text pointer) returning blob (text/image/ntext). This
> means that functions relying on this information (mostly to insert
> partial blobs) does not work. See for instance results on
> freetds.sourceforge.net using protocol 7.3, some tests fail.
> So, as long as you don't use text pointers you are safe until MS
> remove support for protocol 7.3 (mssql 2008) while if you use text
> pointers you are safe until MS remove support for protocol 7.2 (mssql
> 2005).
>
> > Thanks,
> >
> > Geoff Montee
>
> Frediano
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