Обсуждение: Please help - libpq API

Hi all,

I have already posted my query regarding libpq functions and wide character support. Pls somebody help me. I am using libpq API functions in my C code to do operations on the database. But the problem I m facing is API functions like PQexec() etc....accept only char * .... but as part of localization, the queries I want to executed contain chinese characters which are multibytes. So the queries I want to execute are in wchar_t * format and PQ exec() accepts only char *. Is there any alternate way to execute queries having wide characters.

Even if somehow if I convert wchar_t *  to char * and provide it to Postgres, how will it differentiate between chinese characters and normal characters ??

Please help !!

Regs,
Pradeep

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Hi,

I think that this is the wrong list for your problem. My suggestions:

contact pgsql-hackers or check the lists in the postgresql.org page, you will prolly find one list to suit with this.
or
irc.freenode.net, join #postgresql . Good boys lurking there, you will have to fight, but help will be given if you have good maners and offer a pizza.

Good luck.

G.-




--
"Adopting the position that you are smarter than an automatic
optimization algorithm is generally a good way to achieve less
performance, not more" - Tom Lane.

On Wed, Sep 07, 2005 at 11:40:57PM -0700, Pradeepkumar, Pyatalo (IE10) wrote:

> I have already posted my query regarding libpq functions and wide character
> support. Pls somebody help me. I am using libpq API functions in my C code
> to do operations on the database. But the problem I m facing is API
> functions like PQexec() etc....accept only char * .... but as part of
> localization, the queries I want to executed contain chinese characters
> which are multibytes. So the queries I want to execute are in wchar_t *
> format and PQ exec() accepts only char *. Is there any alternate way to
> execute queries having wide characters.

I think you could be using PQexecParams() and passing your wide-char
strings as binary parameters somehow.  I don't really know if this will
work or not, but it may give you an idea.  But note below:

> Even if somehow if I convert wchar_t *  to char * and provide it to
> Postgres, how will it differentiate between chinese characters and normal
> characters ??

Please note that any string you pass from the client will be interpreted
using the client_encoding setting.  So maybe what you have to do is just
set client_encoding to the encoding that the strings are encoded in.  If
you choose the wrong client_encoding, the server may recode the
characters inappropiately, or not at all, and thus insert wrong data.

Please see the documentation.

--
Alvaro Herrera -- Valdivia, Chile         Architect, www.EnterpriseDB.com
"When the proper man does nothing (wu-wei),
his thought is felt ten thousand miles." (Lao Tse)

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> On Wed, Sep 07, 2005 at 11:40:57PM -0700, Pradeepkumar, Pyatalo (IE10) wrote:
>> Even if somehow if I convert wchar_t *  to char * and provide it to
>> Postgres, how will it differentiate between chinese characters and normal
>> characters ??

> Please note that any string you pass from the client will be interpreted
> using the client_encoding setting.  So maybe what you have to do is just
> set client_encoding to the encoding that the strings are encoded in.

I think his problem is that his data is represented in UCS2 or UCS4
(or some other fixed-width representation) and we don't support those
as client_encoding values AFAIK.  He'll need to do an encoding
conversion to some representation we do support, such as UTF8.

            regards, tom lane

Hi all,

Thanks for all your patience and help. I really appreciate this group as I
have always found someone or the other replying to my questions. For my
problem, I set the client and server encoding to UNICODE. The problem that
libpq functions does not support wide characters still remains. I am
converting the wide character strings to proper UTF-8 format and passing it
to the libpq functions. But I still feel that libpq functions should support
wide character datatypes also.

Regs,
Pradeep

-----Original Message-----
From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
Sent: Thursday, September 08, 2005 10:17 PM
To: Alvaro Herrera
Cc: Pradeepkumar, Pyatalo (IE10); pgsql-admin@postgresql.org;
pgsql-novice@postgresql.org
Subject: Re: [ADMIN] Please help - libpq API

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> On Wed, Sep 07, 2005 at 11:40:57PM -0700, Pradeepkumar, Pyatalo (IE10)
wrote:
>> Even if somehow if I convert wchar_t *  to char * and provide it to
>> Postgres, how will it differentiate between chinese characters and
>> normal characters ??

> Please note that any string you pass from the client will be
> interpreted using the client_encoding setting.  So maybe what you have
> to do is just set client_encoding to the encoding that the strings are
encoded in.

I think his problem is that his data is represented in UCS2 or UCS4 (or some
other fixed-width representation) and we don't support those as
client_encoding values AFAIK.  He'll need to do an encoding conversion to
some representation we do support, such as UTF8.

            regards, tom lane