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  • From: "Bullock, Owen" <Owen.Bullock AT broadridge.com>
  • To: FreeTDS Development Group <freetds AT lists.ibiblio.org>
  • Subject: Re: [freetds] bcp issue with TDS 5.0, Sybase, and long rows
  • Date: Tue, 13 Aug 2013 16:06:43 +0100

Thanks Frediano,

I downloaded that tar, but it doesn't appear to have your 5th May patch in
it.

So I looked it up on Git and applied to tds.h and bulk.c and it looks good -
many thanks!

Owen

-----Original Message-----
From: freetds-bounces AT lists.ibiblio.org
[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of Frediano Ziglio
Sent: 12 August 2013 19:00
To: FreeTDS Development Group
Subject: Re: [freetds] bcp issue with TDS 5.0, Sybase, and long rows

Hi Owen,
it's a known issue fixed on 5 May this years, both on 0.91 and master
branches.

Last 0.91 snapshot is at
ftp://ftp.freetds.org/pub/freetds/stable/freetds-0.91.89.tar.bz2.

Frediano


2013/8/12 Bullock, Owen <Owen.Bullock AT broadridge.com>

>
> Apologies in advance for the long post, hopefully its of interest to
> someone.
>
>
> I'm in the process of moving some old C/Sybase db-lib code over to
> FreeTDS but I've run into an issue when we're programmatically bcp'ing
> long table rows ( > 255 chars) which are nullable. The bcp either
> fails or garbles my data.
>
> I've read what I can on the bulk copy offset/adjustment table (
> http://freetds.schemamania.org/tds.html#p7), and fired up Ribo so I
> could compare packets between Sybase and FreetDS.
>
> Its apparent that the Sybase library calculates the high-byte
> adjustment table rather differently to FreeTDS. (Perhaps FreeTDS is
> more mssql focussed here? Or have Sybase changed this recently? - I'm
> running on Sybase 15.7 and can confirm this is the same back to 12.5
> but that's the oldest I have access to)
>
> Has anyone else run into this issue? (I suspect not many people are
> doing this on Sybase - we're motivated by the need for Bigint support
> on our old dblib code)
>
>
> example - I'm copying a row of 5 columns into a table composed of
> char(255) columns. These are the calculated offsets:
>
> 0068
> 00CC
> 0130
> 0131
> 0132
>
> FreeTDS calculates (correctly, as per spec) the offset/adjustment
> table as
> this:
>
> 1+ncols Adjustment Offset
> +--------+-------------------+-------------------+
> | 06 | 01 01 01 00 00 00 | 32 31 30 cc 68 04 |
> +--------+-------------------+-------------------+
>
> However, the Sybase lib sends this:
>
> 1+ncols Adjustment Offset
> +--------+-------------------+-------------------+
> | 06 | 04 | 32 31 30 cc 68 04 |
> +--------+-------------------+-------------------+
>
>
> The adjustment table is hugely different, and of course my data gets
> garbled when I send it using FreeTDS.
>
> After some analysis of various scenarios - it seems to me that Sybase
> is indicating the column number where the high-order byte *changes*
> (unless its the last column - in which case it just drops it.) I'd
> welcome other peoples thoughts on this.
>
>
>
> Here's a couple more examples to show this:
>
> 1+ncols Adjustment Offset
> +--------+-------------------+-------------------+
> FreeTDS | 06 | 01 01 00 00 00 00 | 32 31 cd cc 68 04 |
> Sybase | 06 | 05 | 32 31 30 cc 68 04 |
> +--------+-------------------+-------------------+
>
> - change in column 5
>
>
> 1+ncols Adjustment Offset
> +--------+-------------------+-------------------+
> FreeTDS | 06 | 04 04 04 02 01 00 | 7a 79 78 fc 80 04 |
> Sybase | 06 | 04 04 03 02 | 32 31 30 cc 68 04 |
> +--------+-------------------+-------------------+
>
> - in the above one the offset goes from 0x2fc to 0x478, so Sybase
> indicates this high jump of two by putting 04 in the adjustment table twice.
>
>
> 1+ncols Adjustment Offset
> +--------+-------------------+-------------------+
> FreeTDS | 04 | 01 00 00 00 | 30 cc 68 04 |
> Sybase | 04 | | 30 cc 68 04 |
> +--------+-------------------+-------------------+
>
> - high-byte change is the last column so Sybase doesn't mention it. This
> also happens if the following cols are null and empty
>
>
>
> In my code this saves only a handful of bytes, but i guess if you've
> got long rows with many columns then you'd start to see some advantage.
>
>
> Any thoughts?
>
> regards,
> Owen
>
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