Re: [HACKERS] Troubles using German Umlauts with JDBC - Mailing list pgsql-jdbc

On Sun, 9 Sep 2001 10:24:32 -0400 (EDT), Bruce Momjian wrote:
>I can add something if people agree there is an issue here.

IMO the issue is twofold. Without multibyte compiled in:

1) the server cannot tell the client which single byte character
encoding is being used, so a client like JDBC cannot properly
convert to its native encoding

2) its not possible to create a database with a single byte
encoding other than ASCII (see my posting
http://fts.postgresql.org/db/mw/msg.html?mid=1029462)

I'm not sure to what extent these issues are related.

Also, client/server character conversion is coupled to multibyte
support (see Peter's reply to my posting). This may be a
limitation for other clients, but I'm not sure about that.

Basically, it seems that multibyte support is adding features
that are needed in single byte environents as well. Perhaps the
problem can be solved by documentation (recommending to enable
multibyte support in non-ASCII singlebyte environments), perhaps
by an alias (--enable-character-encoding), perhaps the
functionality needs to be split into a true multibyte part and a
generic part. I don't know what's best, this probably depends on
the "price" of compiling in multibyte support.

Regards,
René Pijlman

>> I've added a new section "Character encoding" to
>> http://lab.applinet.nl/postgresql-jdbc/, based on the
>> information from Dave and Barry.
>>
>> I haven't seen a confirmation from pgsql-hackers or Bruce yet
>> that this issue will be added to the Todo list. I'm under the
>> impression that the backend developers don't see this as a
>> problem.
>>
>> Regards,
>> Ren? Pijlman
>>
>> On Tue, 04 Sep 2001 10:40:36 -0700, Barry Lind wrote:
>> >I would like to add one additional comment.  In current sources the jdbc
>> >driver detects (through a hack) that the server doesn't have multibyte
>> >enabled and then ignores the SQL_ASCII return value and defaults to the
>> >JVM's character set instead of using SQL_ASCII.
>> >
>> >The problem boils down to the fact that without multibyte enabled, the
>> >server has know way of specifiying which 8bit character set is being
>> >used for a particular database.  Thus a client like JDBC doesn't know
>> >what character set to use when converting to UNICODE.  Thus the best we
>> >can do in JDBC is use our best guess (JVM character set is probably the
>> >best default), and allow the user to explicitly specify something else
>> >if necessary.
>> >
>> >thanks,
>> >--Barry
>> >
>> >Rene Pijlman wrote:
>> >> [forwarding to pgsql-hackers and Bruce as Todo list maintainer,
>> >> see comment below]
>> >>
>> >> [insert with JDBC converts Latin-1 umlaut to ?]
>> >> On 04 Sep 2001 09:54:27 -0400, Dave Cramer wrote:
>> >>
>> >>>You have to set the encoding when you make the connection.
>> >>>
>> >>>Properties props = new Properties();
>> >>>props.put("user",user);
>> >>>props.put("password",password);
>> >>>props.put("charSet",encoding);
>> >>>Connection con = DriverManager.getConnection(url,props);
>> >>>where encoding is the proper encoding for your database
>> >>>
>> >>
>> >> For completeness, I quote the answer Barry Lind gave yesterday.
>> >>
>> >> "[the driver] asks the server what character set is being used
>> >> for the database.  Unfortunatly the server only knows about
>> >> character sets if multibyte support is compiled in. If the
>> >> server is compiled without multibyte, then it always reports to
>> >> the client that the character set is SQL_ASCII (where SQL_ASCII
>> >> is 7bit ascii).  Thus if you don't have multibyte enabled on the
>> >> server you can't support 8bit characters through the jdbc
>> >> driver, unless you specifically tell the connection what
>> >> character set to use (i.e. override the default obtained from
>> >> the server)."
>> >>
>> >> This really is confusing and I think PostgreSQL should be able
>> >> to support single byte encoding conversions without enabling
>> >> multi-byte.
>> >>
>> >> To the very least there should be a --enable-encoding-conversion
>> >> or something similar, even if it just enables the current
>> >> multibyte support.
>> >>
>> >> Bruce, can this be put on the TODO list one way or the other?
>> >> This problem has appeared 4 times in two months or so on the
>> >> JDBC list.
>> >>
>> >> Regards,
>> >> Ren? Pijlman <rene@lab.applinet.nl>
>>
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