[ruby-oci8-devel] About XML DB support in Ruby-OCI8

[KUBO Takehiro]

Hi Liming,

On Wed, Mar 12, 2008 at 12:25 PM, Liming Lian <liming.lian at oracle.com> wrote:
> Hi Kubo,
>
> I am looking into XML DB support in Ruby-OCI8. It is apparent the
> existed code in xmldb.c only implements part of this functionality. And
> it is quite standalone and focuses only on how to construct REXML
> objects from XML data. The missing parts are: defining new data type of
> XMLType for binding, operating XML data in database and some other
> functions related to OCI operations.

Yes. I had implemented oci8_make_rexml() to construct REXML objects
from XML data in Oracle type attributes. It was called from tdo.c,
which was deleted about one year ago. When I reconstructed Oracle
object type support, I didn't add code for XML type. That's because
I thought I would add it after XML type binding was finished.
But it have been postponed.

> Another issue I concern is that, the XML DB support depends on XMLDB
> development toolkit(XDK). We have to check the host environment to
> determine if the XDK is available in the configuration phase.  To check
> prerequisite of XDK installation, I think we have to change the
> ext/oci8/extconf.rb or ext/oci8/oraconf.rb a little bit to generate
> proper Makefile for compiling oci8lib.

As for oci8_make_rexml(), it doesn't need XMLDB headers. Required
function prototypes are copied to xmldb.c.

> Before taking further step into improving XML DB support in OCI8, I
> would like to know your thoughts  including how did you previously plan
> to design xmldb.c, what's the difficulties you have ever met, and does
> this module depends on any other parts in Ruby-OCI8. I believe those
> information is a great of importance to me.

* How did you previously plan to design xmldb.c.

previous plan:
  xmldb.c
   - conversion between REXML objects and XML data

  tdo.c
   - binding XML data
   - get/set XML data in object type attributes

* Does this module depends on any other parts in Ruby-OCI8.

current plan:
  xmldb.c
   - conversion between REXML objects and XML data
   - binding XML data

  object.c
   - get/set XML data in object type attributes

Almost XML type support are implemented in xmldb.c.
 - bind class (OCI8::BindType::REXML?)
 - conversion between XML data and REXML objects

The number of non-static C functions in xmldb.c is only three.
  void Init_oci_xmldb(void);
  VALUE oci8_make_rexml(struct xmlctx *xctx, xmlnode *node);
    construct REXML objects from XML data.
  void oci8_set_rexml(struct xmlctx *xctx, xmlnode *node, VALUE obj);
    1. clear all contents of a XML datum
    2. set REXML object's contents to the XML datum.

object.c uses oci8_make_rexml and oci8_set_rexml to get and set
XML type attributes in Oracle object types.

* What's the difficulties you have ever met.

1. whitespaces

Whitespaces in XML text may or may not be reserved when converting
to DOM objects. I have forgot the details.

2. encoding

REXML's encoding must be UTF-8. But XML type's encoding depends on
NLS_LANG.