Re: XUpdate: how to replace a node?

Hi,

> Hi, I need to replace a given node in my database by a whole new node.
> First, is the XUpdate documentation found on
> http://xmldb-org.sourceforge.net/xupdate/xupdate-wd.html current
> enough?
>
> Well, this documentation doesn't mention any replace functionality. So
> I thought that I could just remove the node, and add the new node to
> the parent, at the same position. Problem: in order to be able to
> append the new node to the parent, I need to put a reference to the
> parent in a variable before deleting the old node: my XPath to the
> node is like //node[@id="2"], so I can easily find the parent before
> deleting the node, but it is impossible afterwards.

I first tried the approach using variables. However, this didn't work, 
basically because the declared variables were not visible from within the 
select. I have thus fixed the code, so the following code snippet does the 
job now (example taken from the corresponding junit test 
"src/org/exist/xupdate/test/modifications/variables.xml"):

<xu:variable name="address" select="//address[lname = 'Hyde']"/>
<xu:variable name="root" select="$address/.."/>
        
<xu:remove select="$address"/>
<xu:append select="$root">
        <address>
                <fname>Boris</fname>
                <lname>Becker</lname>
                <company>BB-Inc.</company>
                <city>Leimen</city>
        </address>
</xu:append>

However, I also added an experimental xupdate:replace command. The code 
differs only slightly from xupdate:update. Using xupdate:replace, you can 
directly do:

<xu:replace select="//address[lname = 'Hyde']">
        <address>
                <fname>Boris</fname>
                <lname>Becker</lname>
                <company>BB-Inc.</company>
                <city>Leimen</city>
        </address>
</xu:replace>

which is definitely much simpler. You will find both changes in the current 
CVS or snapshot.

> I also tried to define the variables in the surrounding xquery, and
> use them from within the xupdate, but I get an error saying "select
> expression should evaluate to a node-set; got xs:integer". This is the
> syntax I used:
> let $node := document('/db/doc.xml')//node[@n='2']
> let $parent := $node/..
>
> let $mods := xmldb:update($root,
>       <xu:modifications version="1.0" xmlns:xu="http://www.xmldb.org/xupdate";>
>               <xu:append select="{$parent}" child="0">
>                       <foo/>
>               </xu:append>
>
>       </xu:modifications>
>
> )

This can't work: the xupdate command uses its own instance of the XPath/XQuery 
engine, so there's no way to pass variables from the XQuery to the XUpdate. 
You would have to pass the XPath for the select as a string. That's why I 
would like to implement the XQuery update extensions.

Wolfgang


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