How to merge nodes?

Hi,
Im using basex, a xml database and I just started doing xquery a month ago and may not use the correct terminology.

I need a sanity check on my idea and also accept alternative solutions.

I have 3 files.

$conf = 5 GB xml file containing the current server configuration

$input= The changes we want to do to $conf, assume each line is a tuple, (unique path to a node and the new value the node should have)

The only way to change the configuration to the server is to upload a configuration file to the server, but because only a fraction of the values might be updated we DO NOT want to want to modify $conf and upload it.

$newConf= The new configuration file containing the updated values from $input and has the same structure as $conf. The file to be uploaded to the server.


So want to create $newConf from $conf and $input.

========= example =============

Generic case scenario, $conf has higher node diversity and depth.
======= $conf
<a>
   <b id="1">
       <c>1</c>
       <c1>1</c1>
       <c2>1</c2>
   </b>
   <b id="2">
       <c>1</c>
       <c1>1</c1>
       <c2>1</c2>
   </b>
   <b id="3">
       <c>1</c>
       <c1>1</c1>
       <c2>1</c2>
   </b>
   <x id="2">
       <c>1</c>
       <c1>1</c1>
       <c2>1</c2>

       <y attr="">

              <z>1</>

       </y>
   </x>
</a>
=================== $input (: Example input, paths and value can be arbitrary :)
(//b[@id eq 1]/c, 2)
(//b[@id eq 1]/c1, 2)
(//b[@id eq 3]/c1, 2)



================= $newConf

(: This file is a result of the input $conf and $input, note that the hiearchy is retained and attributes but only has the updated values from $input :)
<a>
   <b id="1">
       <c>2</c>
       <c1>2</c1>
   </b>
   <b id="3">
       <c1>2</c1>
   </b>

</a>
======= Current plan (: Very rough idea :)

for $line in $input

let $node := extract($conf,$line)

merge($newConf, $node)  (: This is some sort of update function :)

============= Last words

1. Please help me out with the merge function

2. Anything I forgot to consider?

3. I did look up on streaming transform but I dont see advantages over the current plan because it feels like it would be hard to feed the $input file. And my lack of skills in that area.

Thank you for reading,