FreeTDS Development Group

[Brian Bruns <camber AT ais.org>]

>From what I'm seeing, MS is, by default under TDS 7.0, actually sending
the entire text clob all in one go.  So technically they are sticking to
the protocol. It just makes the maxlength value useless for preallocating
memory!  

If freetds were to allow a "set textsize" to be executed automatically on
connect, ct_describe would return a sane value and everyone should be
happy.

Brian

On Mon, 4 Jun 2001, Michael Peppler wrote:

> Brian Bruns writes:
>  > Hmmm... this is a case where DBD::Sybase is dealing with some assumptions
>  > which MS went and changed.  Is the proper place to deal with this your
>  > code or mine?  I'm inclined to make a new config file option "default 
> text
>  > size" and allow users to set it in the freetds.conf file.  Whaddya think?
> 
> Well - I am just using the data as returned by Client Library
> (ct_describe() in this case) and using datafmt.maxlength to effect the
> bind.
> 
> By default Sybase will limit this to 32k (although you can set
> TEXTSIZE to alter that behaviour). If MS returns 2GB for this value,
> but still limits the amount of *data* that it returns to the default
> (or set) TEXTSIZE value then I'd say that it's a bug in MS's
> implementation of the protocol...
> 
> I need to use some value here to allocate a large enough buffer for
> the ct_bind() call, so just using some default value will not work
> (unless the actual data fetch never exceeds that value)
> 
> An upcoming version of DBD::Sybase will have access to ct_get_data()
> and ct_send_data() to allow direct read/write of TEXT/IMAGE columns
> (and to allow read/write in blocks rather than sending the whole thing
> in one go).
> 
> Michael
> 
> 
>  > On Mon, 4 Jun 2001, Michael Peppler wrote:
>  > 
>  > > Darryl Friesen writes:
>  > >  > >> Eric, if you issue the query "set textsize 10000" prior to 
> selecting
>  > >  > >> the text column does that also fix the problem?
>  > >  > >
>  > >  > > Yes it does!  If I just do:
>  > >  > 
>  > >  > Hmm.  Doesn't work for me here.  I still get a
>  > >  > 
>  > >  >     Out of memory during "large" request for -2147479552 bytes
>  > >  > 
>  > >  > in my Perl script (which uses DBD::Sybase)
>  > > 
>  > > I seem to recognize this one... I think MS returns the maximum
>  > > possible size of the object, instead of the actual size, and I use the
>  > > size value to allocate memory for the object in ct_bind() (which of
>  > > course fails in your case).
>  > > 
>  > > Michael
>  > > 
>  > 
>  > 
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