FreeTDS Development Group

[Michael Peppler <mpeppler AT peppler.org>]

Brian Bruns writes:
 > 
 > >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!  

What?!?!

Don't they honour the default TEXTSIZE value?

(oh, and of course they don't allow setting CS_OPT_foo via
ct_options() either, so you have to execute it as a language statement
for that connection)

 > 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.

Yes, I guess so.

Michael


 > 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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 > > 
 > 
 > 
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-- 
Michael Peppler - Data Migrations Inc. - mpeppler AT peppler.org
http://www.mbay.net/~mpeppler - mpeppler AT mbay.net
International Sybase User Group - http://www.isug.com
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