FreeTDS Development Group

["Eric Deutsch" <edeutsch AT systemsbiology.org>]

>A second related problem is that some people are having text problems
>under TDS 7.0, but no seems to care enough to give an example so it be
>fixed. And that is where the CAST(mytextcol as varchar(8000)) would come
>in.

Hi, I care very much about this because my software would be useless if this
remained a problem.  Below is my last post on this subject.  If there's any
additional information I can provide, please let me know.  The problem
occurs for me for any SELECT to any column of type TEXT.  I assume this is
not the case for other versions of SQL Server, so maybe it's just for 2000.
The debugging code I inserted in the patch below could be used to examine
the behavior on other versions of SQL Server to see where the maxlength
started being 2GB.

Please don't hesitate to contact me if I can provide more information.  My
code is working for now, but the hack I inserted to fix it is not a good
solution.

thanks,
Eric


-----Original Message-----
From: bounce-freetds-127899 AT franklin.oit.unc.edu
[mailto:bounce-freetds-127899 AT franklin.oit.unc.edu]On Behalf Of Eric
Deutsch
Sent: Friday, March 30, 2001 10:03 AM
To: TDS Development Group
Subject: [freetds] Re: SqlServer text size limitation


>On Fri, 30 Mar 2001, Guille -bisho- wrote:
>
> I have another problem. Using text fields and protocol version 7.0 and SQL
> Server 7.0 SP3 it says that the server gives a erroneous response.
>
> The protocol 4.2 connect and return queries, but the text fields are
returned
> without the last character.
>
> I'm using FreeTDS 0.51.
>
> Is a known issue??? Is there any patch???
>

Hi, I have been having problems with TEXT fields in the following setup:
Perl 5.6.0 on Linux accessing MS SQL Server 2000
via perl DBI::Sybase + FreeTDS 0.51 + TDS 7.0

If I try to retrieve data from a columntype of TEXT, program crashes with
error "Out of Memory!" (VARCHAR, CHAR, etc. are all fine; indeed if I
SELECT a TEXT field with SUBSTRING(textcolumn,1,8000) all is also well).
But a raw TEXT column is bad news.

I inserted the following hack to fix the problem:

*** ct.c:orig   Sat Nov  4 12:41:43 2000
--- ct.c        Fri Mar 30 09:30:59 2001
***************
*** 743,746 ****
--- 745,756 ----
        datafmt->precision = curcol->column_prec;
        datafmt->scale = curcol->column_scale;
+       tdsdump_log("%L inside ct_describe() datafmt->maxlength = %d,
datafmt->usertype = %d, datafmt->precision = %d, datafmt->scale = %d\n",
datafmt->maxlength, datafmt->usertype, datafmt->precision, datafmt->scale);
+
+         /* FIX ME Deutsch hack */
+         if (datafmt->maxlength > 10000) {
+           datafmt->maxlength=100000;
+           tdsdump_log("%L inside ct_describe() datafmt->maxlength = %d
after artificial limiting\n", datafmt->maxlength);
+         }
+
        /* FIX ME -- TDS 5.0 has status information in the results
        ** however, this will work for 4.2 as well */

----------------

The TDSDUMP output looks like this for me now:

2001-03-30 09:31:37 inside ct_describe()
2001-03-30 09:31:37 inside _ct_get_client_type()
2001-03-30 09:31:37 inside ct_describe() datafmt->datatype = 16 server type
35
2001-03-30 09:31:37 inside ct_describe() datafmt->maxlength = 2147483647,
datafmt->usertype = 0, datafmt->precision = 0, datafmt->scale = 0
2001-03-30 09:31:37 inside ct_describe() datafmt->maxlength = 100000 after
artificial limiting
2001-03-30 09:31:37 inside ct_bind()
2001-03-30 09:31:37 inside ct_bind() item = 2 datafmt->datatype = 16
2001-03-30 09:31:37 inside ct_fetch()


What appears to be happening is that the maxlength for a TEXT field
appears to be getting returned as 2GB, and I assume that some part of the
program is then trying a malloc() 2GB, which is bad.  So my hacked code
just limits this to 100 kB, which is probably fine for my current
purposes.  But obviously, this is not a proper fix.  If a TEXT field
really were larger than 100 kB, the result would be truncated.

Perhaps the experts out there can figure out how to handle this properly
and incorporate into current codebase?

thanks,
Eric



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