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  • From: Norbert Matzke <matzke AT geopp.de>
  • To: FreeTDS Development Group <freetds AT lists.ibiblio.org>
  • Subject: Re: [freetds] SQLBindParameter() does not work with UTF-8 ?!
  • Date: Fri, 10 Oct 2008 18:06:47 +0200

ZIGLIO, Frediano, VF-IT wrote:
ZIGLIO, Frediano, VF-IT wrote:
Problem: My client ODBC application needs to bind
parameters which are
UTF-8 encoded to SQL insert/update statements.
I have set ClientCharset to UTF-8 in freetds.conf.

I did some tests with Version 0.82 of FreeTDS and SQL Server 2005.
Seemed to work, but not with a short UTF-8 String like '€'.
'€' is 3 bytes long in UTF-8 encoding.

If I called
SQLBindParameter( , ,SQL_C_CHAR, SQL_WVARCHAR, n, 0, , , &ind )
with n=1 and *ind=3 I got an error message. iconv was not able to
convert '€' and SQL Server complains also ...

Calling with n=3 and *ind=3 succeeds but inserts the
string '€ ' into
the database because the Server pads with 2 blanks to the requested size
of 3 CHARS.

Setting *ind=SQL_NTS did not help.

I have tested version 0.83dev 2008-10-09 also: It did not work at
all using UTF-8 strings with non single byte UTF-8 characters.

So I have had a look at what is going on inside the FreeTDS code
(ver. 0.83dev) and found that the problem arises due to
insufficient
buffer space for the bounded parameter.

I solved the problem with very small changes to tds/mem.c and
odbc/sql2tds.c (see attached patch). For me it works now.

Any comments on this issue ?

Best regards,
Norbert


It's strange that every time you implement a feature
someone ask for another... well, this means that previous works as expected I hope :)
WVARCHAR is currently in progress. I don't think is
supported by 0.82 and have some problems (there is a failing test) under CVS HEAD. Test related to your problem should be utf8, I'll test with your string.
Actually I'm quite busy so I have no timeline for this issue.

freddy77

I was not aware of the fact that utf-8 support is quite new to FreeTDS.
I have had a look at the documentation before I tried to use it, a few
days ago, and it seemed to me that by setting the Client Charset to
UTF-8 one can use a MS SQL Server like any other UTF-8 capable DMBS --
though MS SQL Server itself is not UTF-8 capable ! This is a very
valuable feature of FreeTDS !

Besides, if I understand correctly, requesting SQL_WVARCHAR vs. SQL_VARCHAR as SQL parameter type does not make any diffence to FreeTDS ? Only the server will not_do/do a USC-2 --> CP1252 --> UCS-2
conversion with the data ? (assuming CREATE TABLE ... NVARCHAR() ..)

Norbert


Well... SQL_WVARCHAR have problems. FreeTDS support UTF-8 as client encoding
converting as best as it can but using SQL_VARCHAR. There is a big difference
between SQL_VARCHAR and SQL_WVARCHAR cause FreeTDS should use VARCHAR or
NVARCHAR on server. Currently not supporting SQL_WVARCHAR means that you have
to use SQL_VARCHAR which lead to VARCHAR so you can't represent much
characters. When FreeTDS will support SQL_WVARCHAR any UCS-2 characters will
be available to your client.

freddy77

That sounds strange to me. I just did another test and found the
following behaviour:

- SQLBindParameter(... SQL_C_CHAR, SQL_WVARCHAR, 7, ..., "utf-8 €", ,&9)
Sending Packet ==> ... P1 NCHAR(7) ...

- SQLBindParameter(... SQL_C_CHAR, SQL_VARCHAR, 7, ..., "utf-8 €", ,&9)
Sending Packet ==> ... P1 CHAR(7) ...

In both cases the iconv is called freetds internal (for the wire
conversion) to UC2-2 with source encoding UTF-8 (due to Client Charset
setting). Data on the wire is the same !
So it should depend only on the server (and the CREATE TABLE column
type) which kind of storage conversion is applied.

Norbert





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