Can I use user defined function in Xquery to replace node value in PLSQL?

Question

I want to change oracle xmltype node value by my function my_calculator but I can't. See there:

set serveroutput on
declare
w_xml xmltype;
begin

SELECT
      XMLQUERY('copy $tmp := .
               modify
                (for $l3 in $tmp//Line3
                    return replace value of node $l3 with my_calculator($l3)
                )
                
                return $tmp'
               PASSING xmltype('<Response><Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>10</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>12</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
</Response>') RETURNING CONTENT)
        into w_xml
        FROM dual;
        dbms_output.put_line( w_xml.extract('/*').getClobVal() );
end;

It return:

Error report -
ORA-19237: XPST0017 - unable to resolve call to function - fn:my_calculator
ORA-06512: at line 5
19237. 00000 -  "XPST0017 - unable to resolve call to function - %s:%s"
*Cause:    The name and arity of the function call given could not be matched with any in-scope function in the static context.
*Action:   Fix the name of the function or the number of parameters to match the list of in-scope functions.

Can I use a user's function in "return replace value of node $l3 with my_calculator($l3)" ? Many thanks.

Answer 1

Because I can not use user function in xquery. So I change my code to use updatexml, It will running ok if the data isn't too large and the DB version in 11,12:

create or replace FUNCTION fn_xmlupdate( var_xpath VARCHAR2, var_rec XMLTYPE,var_attribute varchar2 default 'text()') RETURN XMLTYPE
IS
v_return xmltype;
querystring varchar2(4000);
update_xquery varchar2(200):='$i/text()';
update_query clob;

BEGIN
if  var_attribute!= 'text()' then
    update_xquery:='$i/attribute::*';
end if;
querystring:='for $i in $doc'||var_xpath||'/descendant-or-self::*
            let $path := $i/string-join(ancestor-or-self::*/name(.), ''/'')
            return <data>{attribute path {concat($path,if (exists($i/attribute::*/name(.))) then 
            concat("[@",$i/attribute::*/name(.),"=",$i/attribute::*,"]","/'||var_attribute||'") else())}, attribute value {'||update_xquery||'}}</data>' ;
            
--dbms_output.put_line(querystring);

select --listagg(path_value,',') within group (order by rownum) update_query 
'select updatexml(:var_rec,'||listagg(path_value,',') within group (order by rownum)||')
from dual '
into  update_query
from
(select ''''||xpath||''','|| MY_TRANSFORM(text) path_value
from   
       XMLTable( 
         querystring
         PASSING var_rec AS "doc"
         COLUMNS xpath varchar2(4000) path '/data/@path', 
                 text  varchar2(4000) path '/data/@value'
       )
);
--dbms_output.put_line(update_query);

execute immediate update_query  into v_return using var_rec;


RETURN v_return;
END;

If you want update note value:

 fn_xmlupdate(path,xmltype)

If you want update attribue value

fn_xmlupdate(path,xmltype,@attribute_name)

Answer 2

You can't call pl/sql functions in xpath and xquery. They have own functions and operators: https://www.w3.org/TR/xpath-functions-31/ But you can declare and use own xquery function:

SELECT
      XMLQUERY('declare function local:my_calculator($p) {xs:decimal($p + 100)}; (: eof :)
      copy $tmp := .
               modify
                (for $l3 in $tmp//Line3
                    return replace value of node $l3 with (local:my_calculator($l3))
                )
                return $tmp'
               PASSING xmltype('<Response><Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>10</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>12</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
</Response>') RETURNING CONTENT) as xdata
FROM dual;

Results:

XDATA
----------------------------------------------------------------------------------------------------
<Response>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>110</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>112</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
</Response>

But in this simple case you don't even need PL/SQL functions, just use simple operators:

SELECT
      XMLQUERY('copy $tmp := .
               modify
                (for $l3 in $tmp//Line3
                    return replace value of node $l3 with (xs:integer($l3) + 100)
                )
                
                return $tmp'
               PASSING xmltype('<Response><Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>10</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>12</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
</Response>') RETURNING CONTENT) as xdata
FROM dual;

Results:

XDATA
----------------------------------------------------------------------------------------------------
<Response>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>110</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
  <Card>
    <Address attr_cust="0">
      <Line2>def</Line2>
      <Line3>112</Line3>
      <Line4>jkl</Line4>
      <Line5>mno</Line5>
      <Country/>
    </Address>
  </Card>
</Response>