Re: [PATCH] Add XMLText function (SQL/XML X038) - Mailing list pgsql-hackers

On 2023-08-26 16:00, Pavel Stehule wrote:
> Saxon can be an interesting library, but nobody knows if integration
> with
> Postgres is possible. Their C implementation is Java compiled/executed
> by GraalV.

Indeed, such an integration would probably not be in core.

Of the two possible-ways-forward described on that wiki page, the one
that didn't rely on the defunct XQC was one involving query rewriting.
Have the parser understand the SQL/XML customized syntax, and define
a set of ordinary functions it will be rewritten into. (This idea is
bolstered somewhat by the fact that many things in SQL/XML, XMLTABLE
for example, are /defined in the standard/ in terms of query rewriting
into calls on simpler functions.)

Then let there be an extension, or ideally someday a choice of
extensions, supplying those functions.

As to whether running Saxon in a Postgres extension is possible, that's
been an example that ships with PL/Java since 1.5.1 five years ago.

It's too bad the other projects have stalled; it's good to have more
than one ready option. But Saxon shows no sign of going away.

Perhaps the act of devising a standardized rewriting of queries
onto a standardized set of loadable functions could be of interest
to other DBMS projects as well. It's hard to imagine another DBMS
not being in the same boat (if it isn't from a rich commercial firm
that happens to have a modern XQuery implementation in-house).

Maybe having that set of functions specified, with the prospect
that more than one DBMS might be interested in a project
implementing them, even inspires someone to go look at the
xqilla or zorba repos to see how far they got, and pick up
the baton, and then there could be more than one option.

Regards,
-Chap