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

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

On 1/25/07, matilda matilda <ma...@gr...> wrote:
> Hi Anthony,
>
> >>> "Anthony Tuininga" <ant...@gm...> 25.01.07 17.12 Uhr
> >>>
> >I'm not sure what you mean by this. Could you explain further?
> >Currently cx_Oracle expects you to have to deal with everything. You
> >must pass in a stream of characters (not unicode) and you will get
> >back the same. That should be changed -- once I get my head around
> >everything, of course. :-)
>
> Ok, my conclusion until now:
> 1) At the moment you can forget python unicode strings
> and the direct handling of them concering binding them to
> oracle table columns.

Correct.

> 2) At the moment the allocated buffers for defined variables
> (db->client) and the buffer hint for the server side while
> binding (client->db) is done in a simple 1-to-1-fashion.
> That's ok, as long as the byte representation of a character
> string has the same length as the characterstring itself.

Correct.

> 3) Problems arise as soon as the byte representation is
> dfferent on both sides.
> a) While defining and allocating a variable on the client side
> (db->client) you should take care about the Attributes "isVariableSize"
> and "MaxBytesPerChar" for byte buffer allocation. This could be done
> quite soon, I think :-))

Yes, it can.

> b) While binding a variable (update/insert-statment) code should care
> about giving the server side a correct hint (better more than less) for
> the size of the server side byte representation after converting the
> incomming character stream to the byte representation of the
> related database encoding. (This is a db attribute. Don't know if
> there's
> a similar OCI call to get somthing like MaxBytePerChar).

This is uncertain as to whether or not this can be accomplished
without access to a unicode string in Python. If you have suggestions
as to which OCI calls to make, let me know.

> c) Forget the assumption that the python byte string can be max of 4000
> bytes to fit into a varchar2(4000) column. It can be more if the client
> side
> representation is bigger than the db side representation. This can be
> done
> really now! :-)))

Character semantics would allow for this. I'll have to see if this is
going to cause a problem at all.

> 4) Ask if I can help you. I really need the corrections and I hoped you
> could
> hit the right statements in your code much quicker than I can. Or I
> start to
> change your code and it will start to  be an ugly mess of c
> statements...
> ...then you can forget your nice object oriented coding style.  :-)

I can make the changes and test them somewhat but I would be happy if
you could test them more thorougly given your needs. If you're in a
very big hurry feel quite free to make any changes to your local copy
and then send me the patches (diffs). I can then integrate them
without having to figure everything out myself. What is your pleasure?

I think we should take this off the list now unless there is something
from which all would benefit. A final message in this thread can be
sent when the problems are resolved to your satisfaction.

> Best regards
> Andreas Mock
>
>
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