add xml support function

On Thu, Dec 31, 2009 at 3:33 AM, fangfang liu <yisuoyanyu888@gmail.com> wrote:

Hi - Does anyone know how to add a xml support function into postgresql?

I want to add a function named xmlquery into postgresql.

I modify gram.y by adding xmlquery relatedcode wherever other xml support
functions appear.
but the parser can not find xmlquery, the makeXmlExpr is not called at all.

How about CREATE OR REPLACE FUNCTION xmlquery(...) ?

If that doesn't meet your needs, you'll need to explain what you're
trying to do - and probably provide a patch showing what you've tried
so far.

...Robert

Actually, I expect the function looks like xmlquery(xmlcontent,xquery) and
return the query result.
So xmlconcat(xml1,xml2) become a good example to study.

starting from gram.y, I try to make parser to call xmlquery,the following is
the result of diff:

diff gram.y c:\new_gram.y
449c449
<       XMLPI XMLQUERY XMLROOT XMLSERIALIZE
---

XMLPI XMLROOT XMLSERIALIZE

8270,8273d8269
< | XMLQUERY '(' expr_list ')'
< {
< $$ = makeXmlExpr(IS_XMLQUERY, NULL,
NIL,$3);
< }
8287d8282
<
9296d9290
< | XMLQUERY

IS_XMLQUERY is added in primenodes.h

but the parser can not find xmlquery, the makeXmlExpr is not called at all.

thanks
2009/12/31 Robert Haas <robertmhaas@gmail.com>

On tor, 2009-12-31 at 19:22 +0800, fangfang liu wrote:

Actually, I expect the function looks like xmlquery(xmlcontent,xquery)
and return the query result.

You don't need to modify the parser for that at all. You can implement
that in user-space as a user-defined function.

you mean create and replace funtion xmlquery()?
maybe you are right, but I still want to know why parser does not find
xmlquery.

thanks.

2009/12/31 Peter Eisentraut <peter_e@gmx.net>

fangfang liu wrote:

you mean create and replace funtion xmlquery()?
maybe you are right, but I still want to know why parser does not find
xmlquery.

We would have to see your code to know why it didn't do what you expect.

What exactly are you intending that this function would do anyway? If
you're looking at XQuery support, there are serious issues regarding
what library to use, see
<http://archives.postgresql.org/pgsql-hackers/2009-11/msg01445.php&gt;

cheers

andrew

fangfang liu escribi�:

IS_XMLQUERY is added in primenodes.h

but the parser can not find xmlquery, the makeXmlExpr is not called at all.

Did you add it to keywords.c etc?

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

yes,whereever xmlconcat appears.

2009/12/31 Alvaro Herrera <alvherre@commandprompt.com>

thanks for Xquery info, I do not start to implenment the xmlquery() itself ,
maybe call xqilla lib or sth else in the future.
I think xmltable is almost equal to xmlquery , except that it retuns
talbeset insead of xml.

I take xmlconcat as an example , add xmlquery whereever xmlconcat appers and
nothing else.
the first problem is , I have to make xmlquery accepted by the parser.

2009/12/31 Andrew Dunstan <andrew@dunslane.net>

Sorry,guys, my mistakes, the keywords list should be sorted , and I
just append xmlquery at the end of keyword list , that is why parser does
not call makexmlexpr.Instead, the parser try to find a function to match
xmlquery and faild.

2009/12/31 fangfang liu <yisuoyanyu888@gmail.com>