Re: SQL/XML extension

Dear PostreSQL hackers,

For the interested, here:
http://www.cs.utwente.nl/~hiemstra/courses/reports/sqlxml.pdf
you find a little report discussing possibilities to implement the
SQL/XML standard using the PostgreSQL extension mechanism. The report is
written by Master students following the course "XML & Databases" at U
Twente. Comments are welcome. (I am not on the developers list, so
please reply to my personal email as well)

Best regards,
Djoerd.

--
Djoerd Hiemstra
University of Twente
Department of Computer Science
PO Box 217, 7500 AE
Enschede, The Netherlands

URL: www.cs.utwente.nl/~hiemstra
Tel: +31 53 4892335

Djoerd,

>    http://www.cs.utwente.nl/~hiemstra/courses/reports/sqlxml.pdf
> you find a little report discussing possibilities to implement the
> SQL/XML standard using the PostgreSQL extension mechanism. The report is
> written by Master students following the course "XML & Databases" at U
> Twente. Comments are welcome. (I am not on the developers list, so
> please reply to my personal email as well)

Cool, thanks!

Is this something that somebody is actually working on, or just the paper?

--
Josh Berkus
Aglio Database Solutions
San Francisco

Paul, Rob,

I just read with some interest your paper on XML queries with PostgreSQL.
I'm particularly puzzled by some of your conclusions, and thought you might
want to discuss them with the PGSQL-Hackers mailing list.

Particulary:
Functions should be able to have a variable amount of arguments.

I find this conclusion odd, because function overloading (that is, the idea
that a function is defined by the combination of its name and the number and
type of arguments) is now enshrined in the SQL2003 standard. Of course,
I wouldn't be at all surprised to find out that the SQL committee had broken
their own standard. ;-)

Re-defining AS would, as you notice, break many things. However, you could
easily get around this through quoting. While that would not be exactly
adherent to the standard, it's easier that re-writing the parser.

In some ways, it seems to me that SQL/XML might be better defined as a
separate interface to the database; that is, it's own "shell" which is
incompatible with SQL (since the committee seems to have deliberately made it
incompatible).

Thoughts?

--
Josh Berkus
Aglio Database Solutions
San Francisco

I'm thinking about GiST approach http://www.cs.arizona.edu/xiss/

Oleg
On Thu, 18 Aug 2005, Djoerd Hiemstra wrote:

> Dear PostreSQL hackers,
>
> For the interested, here:
> http://www.cs.utwente.nl/~hiemstra/courses/reports/sqlxml.pdf
> you find a little report discussing possibilities to implement the SQL/XML
> standard using the PostgreSQL extension mechanism. The report is written by
> Master students following the course "XML & Databases" at U Twente. Comments
> are welcome. (I am not on the developers list, so please reply to my personal
> email as well)
>
> Best regards,
> Djoerd.
>
>

Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83

IIRC, Peter Eisentraut noted a while ago that implementing the SQL/XML
functions properly would require building them into the postgresql
parser as special cases. That of course would mean we wouldn't be using
the extension mechanism, and is something we should normally shy away
from, but I think it could be contemplated for something that is in the
standard.

The paper does not seem to have addressed the issue of how this could be
done other than bu using the extension mechanism - that seems a bit of a
pity, although maybe that's exactly the topic they were set.

cheers

andrew

Josh Berkus wrote:

>Paul, Rob,
>
>I just read with some interest your paper on XML queries with PostgreSQL.
>I'm particularly puzzled by some of your conclusions, and thought you might
>want to discuss them with the PGSQL-Hackers mailing list.
>
>Particulary:
>Functions should be able to have a variable amount of arguments.
>
>I find this conclusion odd, because function overloading (that is, the idea
>that a function is defined by the combination of its name and the number and
>type of arguments) is now enshrined in the SQL2003 standard. Of course,
>I wouldn't be at all surprised to find out that the SQL committee had broken
>their own standard. ;-)
>
>Re-defining AS would, as you notice, break many things. However, you could
>easily get around this through quoting. While that would not be exactly
>adherent to the standard, it's easier that re-writing the parser.
>
>In some ways, it seems to me that SQL/XML might be better defined as a
>separate interface to the database; that is, it's own "shell" which is
>incompatible with SQL (since the committee seems to have deliberately made it
>incompatible).
>
>Thoughts?
>
>
>

Dear Josh and Andrew,

Thanks for the prompt replies. For now it's just a paper. It was Rob and
Pim's mission to find out if the SQL /XML standard can be implemented
using the postgresql extension mechanism. Building it into the parser was
no option.

Best, Djoerd.

On Thu, 18 Aug 2005, Andrew Dunstan wrote:

>
> IIRC, Peter Eisentraut noted a while ago that implementing the SQL/XML
> functions properly would require building them into the postgresql
> parser as special cases. That of course would mean we wouldn't be using
> the extension mechanism, and is something we should normally shy away
> from, but I think it could be contemplated for something that is in the
> standard.
>
> The paper does not seem to have addressed the issue of how this could be
> done other than bu using the extension mechanism - that seems a bit of a
> pity, although maybe that's exactly the topic they were set.
>
> cheers
>
> andrew
>
> Josh Berkus wrote:
>
> >Paul, Rob,
> >
> >I just read with some interest your paper on XML queries with PostgreSQL.
> >I'm particularly puzzled by some of your conclusions, and thought you might
> >want to discuss them with the PGSQL-Hackers mailing list.
> >
> >Particulary:
> >Functions should be able to have a variable amount of arguments.
> >
> >I find this conclusion odd, because function overloading (that is, the idea
> >that a function is defined by the combination of its name and the number and
> >type of arguments) is now enshrined in the SQL2003 standard. Of course,
> >I wouldn't be at all surprised to find out that the SQL committee had broken
> >their own standard. ;-)
> >
> >Re-defining AS would, as you notice, break many things. However, you could
> >easily get around this through quoting. While that would not be exactly
> >adherent to the standard, it's easier that re-writing the parser.
> >
> >In some ways, it seems to me that SQL/XML might be better defined as a
> >separate interface to the database; that is, it's own "shell" which is
> >incompatible with SQL (since the committee seems to have deliberately made it
> >incompatible).
> >
> >Thoughts?
> >
> >
> >
>

"Andrew Dunstan" <andrew(at)dunslane(dot)net> wrote
>
> IIRC, Peter Eisentraut noted a while ago that implementing the SQL/XML
> functions properly would require building them into the postgresql parser
> as special cases. That of course would mean we wouldn't be using the
> extension mechanism, and is something we should normally shy away from,
> but I think it could be contemplated for something that is in the
> standard.
>

I guess the reason why SQL/XML should be built into the main parser is the
same as PL/PGSQL. But how did DB2 make it in an extendor way(
http://www-306.ibm.com/software/data/db2/extenders/xmlext/ )? Maybe they
have two copies of SQL parser, one has the basic SQL grammar, the other is
the basic SQL grammar plus or integrated with XML support, once XML extendor
is installed, the basic one will be replaced?

Regards,
Qingqing

Is there any more XML activity that people are working on this area?

---------------------------------------------------------------------------

Djoerd Hiemstra wrote:
> Dear PostreSQL hackers,
>
> For the interested, here:
> http://www.cs.utwente.nl/~hiemstra/courses/reports/sqlxml.pdf
> you find a little report discussing possibilities to implement the
> SQL/XML standard using the PostgreSQL extension mechanism. The report is
> written by Master students following the course "XML & Databases" at U
> Twente. Comments are welcome. (I am not on the developers list, so
> please reply to my personal email as well)
>
> Best regards,
> Djoerd.
>
> --
> Djoerd Hiemstra
> University of Twente
> Department of Computer Science
> PO Box 217, 7500 AE
> Enschede, The Netherlands
>
> URL: www.cs.utwente.nl/~hiemstra
> Tel: +31 53 4892335
>
>
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> TIP 6: explain analyze is your friend
>

--
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SRA OSS, Inc. http://www.sraoss.com

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