FreeTDS Development Group

["ZIGLIO, Frediano, VF-IT" <Frediano.Ziglio AT vodafone.com>]

> 
> I'm always surprised when I can corrupt a table at will.  I'm 
> not quite
> sure of the details yet, but something in our bcp for TDS 5.0 
> is currently
> able to load data into a table that can't be selected back out.  
> 

Probably BCP packet use the same format as server and server doesn't do
much input testing (BCP is used mainly for speed).

> After loading the table with my test program, neither sqsh 
> nor Sybase's
> isql can select the row.  The TDSDUMP and tcpdump records agree, and
> Sybase's Ribo tool also cannot decode the stream.  
> 
> 1> select * from T
> 2> go
>  t           r                    s                             
>  ----------- -------------------- ------------------------------
>            1             1.100000 one                           
>            2             2.200000 two                           
>         NULL             3.300000 three                         
>            4             4.400000 four                          
>            0             5.500000 five                          
>            6             2.075256                               
> Open Client Message
> Layer 0, Origin 0, Severity 78, Number 52
> Unknown marker
> 
> And here's the last bit of the packet:
> 
>       -- the "five" row
> d1 
> 04    00 00 00 00 
> 04    00 00 b0 40 
> 04    66 69 76 65 
> 

All fields are nullable, isn't it ??
I think you can post freebcp input file.

>       -- the "six" row
> d1 
> 04    06 00 00 00 
> 03    00 d1 04 

03 ??? so a float of 3 bytes??? Quite strange...

> 07    00 00 00 04 66 66 f6 
> 
> 40 01 30 ????
> ^^  FreeTDS reports 0x40 as the "unknown marker"
> 
>       -- the "eight" row
> d1    
> 04    08 00 00 00 
> 04    cd cc 0c 41 
> 05    65 69 67 68 74 
> 
> fd 10 00 02 00 08 00 00 00
> 
> The problem appears to be that the "six" and "seven" rows are actually
> missing some bytes:
> 
>       -- the "six" row
> d1 
> 04    06 00 00 00 
> 03    00 
>       -- oops! 
> 
> d1 
> 04    07 00 00 00 
> 04    66 66 f6 40 
> 01    30
>       -- more oops: the data should be 'seven'
> 
> Here's a clue:
> 
> [25] alex.FreeTDS.1> sp_layout T
> [25] alex.FreeTDS.2> go
>  ColumnName Type                      Length      Nulls
>  ---------- ------------------------- ----------- -----
>  t          int                                 4   Y  
>  r          real                                4   Y  
>  s          varchar                            30   N  
>                                                    ^^^ not NULL! 
> 
> 
> 1> select t, coalesce(s, "s can't be null") from T where t = 6 
> 2> go
>  t                                         
>  ----------- ------------------------------
>            6 s can't be null               
> 
> Apparently, we can load a NULL into a non-NULL column.  
> There's logic in
> bcp.c to prevent that, and you'd think think the server would 
> object!  But
> it doesn't, and there's no appropriate message in 
> master..sysmessages, so
> it looks like it's the client's obligation to get right.  
> 
> Back to the rockpile.  
> 

freddy77