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