Re: [cx-oracle-users] Problem with internal buffer sizes

[Anthony T. <ant...@gm...>]

On 1/23/07, matilda matilda <ma...@gr...> wrote:
> Hi Anthony,
>
> thanks for your fast answer. But I really get used to it.  :-))
> Probably you can remember me as I contacted you by private
> mail the first time. So, you see, I follow your abuse and mail to
> the mailing list.  :-))

You're welcome. And yes, thanks for posting to the mailing list for
the enlightenment (or confusion) of all. :-)

> How can I circumvent this problem? How can I even manually increase
> the buffers?

You cannot, unfortunately.

> As far as I know, sqlplus does really double the internal buffers
> to do the communication for the following szenario:
> DB character set is Latin1 => I can store a maximum of 4000
> German umlauts to the a string column. That results in 8000
> bytes on the client side if there is a multibyte encoding enabled.

Hmm, that's worth trying, I suppose. Would you be able to provide a
small test case that demonstrates the problem? Something that has 4000
characters in it which will actually result in considerably larger
number of bytes. I can then try that and see if your assumption is
correct. If it is, then the matter is fairly simple to address.

> How is the buffer size chosen for simple varchar2 columns in
> cx_Oracle?

The database provides that information. Unfortunately, Oracle is not
consistent in terms of whether bytes or characters are returned -- the
problem of having developed much of the code before Unicode was very
widespread. :-(

> Best regards
> Andreas Mock
>
>
>
> >>> "Anthony Tuininga" <ant...@gm...> 23.01.2007 17:24
> >>>
> Currently only LOBs use the environment's "maxBytesPerCharacter"
> specification. Unfortunately (as far as I know -- please correct me if
> I am wrong) varchar2 buffers are limited to 4000 bytes and are
> specified in bytes, not characters. So you may be able to get away
> with increasing the buffer size for small strings but for large
> strings bad things will start to happen. :-) I'm not sure if there is
> a reasonable way around this or not. If anyone cares to enlighten me
> I'd be happy to learn. Anyone??
>
> On 1/23/07, matilda matilda <ma...@gr...> wrote:
> > Hi all, hi Anthony,
> >
> > I have the following problem:
> >
> > The Oracle database I'm using has the internal encoding
> > WE8ISO8859P1. The frontend (shell, python) has the
> > default encoding UTF-8 (NLS_LANG=GERMAN_GERMANY.UTF8).
> > The Oracle client library is handling encoding convertion, BUT:
> > If I fetch a varchar2 (byte) column consisting of a character
> > that is encoded with two bytes in UTF-8, I get the following
> > error while fetching:
> >
> > cx_Oracle.DatabaseError: column at array pos 0 fetched with error:
> > 1406
> >
> > I think it's a problem with internal buffers of the bind variables.
> >
> > 1) What can I do to get rid of that without changing NLS_LANG?
> > 2) Is there or probably will there a way to transparently circumvent
> > this problem. (automatic claiming of bigger buffers).
> >
> > Thanks in advance
> > Andreas Mock
> >
> >
> >
> >
> >
> >
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