XQuery node-name（）函数，它如何工作？

Question

I want add additional pairs for each pair .
I have this kind of code:

<data>
<pair>
    <key>keyName1</key>
    <value>something1</value>
</pair>
<pair>
    <key>keyName2</key>
    <value>something2</value>
</pair>
<pair>
    <key>keyName3</key>
    <value>
            <listOfPairs>
                <pair>
                    <key>keyName4</key>
                    <value>Something6</value>
                </pair>
            </listOfPairs>
    </value>
</pair>
<pair>
    <key>keyName5</key>
    <value>Something9</value>
</pair>
</data>

and I need insert other pairs after each pair no matter in which level, with prefix: "copy" with different value:

<data>
<pair>
    <key>keyName1</key>
    <value>something1</value>
</pair>
<pair>
    <key>copy_keyName1</key>
    <value>another1</value>
</pair>
<pair>
    <key>keyName2</key>
    <value>something2</value>
</pair>
<pair>
    <key>copy_keyName2</key>
    <value>another2</value>
</pair>
<pair>
    <key>keyNamedwithLists</key>
    <value>
        <listOfPairs>
            <pair>
                <key>keyName4</key>
                <value>Something6</value>
            </pair>
            <pair>
                <key>copy_keyName4</key>
                <value>Another6</value>
            </pair>
        </listOfPairs>
    </value>
</pair>
<pair>
    <key>keyName5</key>
    <value>Something9</value>
</pair>
<pair>
    <key>copy_keyName5</key>
    <value>another9</value>
</pair>
</data>

For this kind of result to get, i need to use function: node-name() ? How does it work? How I should use it? Ore maybe I should use another function?

Answer 1

As @jens-erat mentioned, you don't need node-name() , instead presumably you want something like this:

<data> {
for $pair in /data/pair
return
    ($pair,
    <pair>
        <key>{concat("copy_", $pair/key)}</key>
        <value>some other value</value>
    </pair>)
}</data>

UPDATE - As you mentioned in your comment, that will only copy the outer-most pairs, if you want to copy all pairs no matter their depth, then you need to use a recursive descent to transform the input.

I actually found writing this in XQuery for your particular use case quite a challenge, although the solution is rather elegant I think :-) I would be interested if anyone else can think of a better implementation?

xquery version "1.0";

declare function local:copy-pair($pair as element(pair), $copying) as element(pair)+ {
    (
        if(not($copying))then
            $pair
        else(),
        <pair>
            <key>{concat("copy_", $pair/key)}</key>
                { local:recursive-descent($pair/key/following-sibling::node(), true()) }
            </pair>
    )
};

declare function local:recursive-descent($nodes, $copying) {
    for $node in $nodes
    return
        (
        typeswitch($node)
            case element(pair) return
                local:copy-pair($node, $copying)

            case element() return
                element {node-name($node)} {
                    local:recursive-descent($node/node(), $copying)
                }

            case text() return
                if($copying and $node/parent::value and empty($node/parent::value/element()))then
                    text { concat("SOME NEW VALUE. old value = ", $node) }
                else
                    $node

            default return
                (
                    $node,
                    local:recursive-descent($node/node(), false())
                )
        )
};

local:recursive-descent(/data, false())

The recursive-descent function basically does a left-to-right recursive-descent through the node tree. Any element named pair it passes of to the copy-pair function, otherwise it just copies everything apart from when we have a copy ( $copying ) of a text node within a value element, in this instance it creates a new alternative text value for the copy.

The copy-pair function determines whether to copy the original pair depending on if we are already copying or not and then creates the new copy of the original pair, it then itself performs a recursive descent.

Answer 2

If you have access to XQuery update and the transform expression you can do something like:

declare function local:additional-pairs($d){
 copy $c:=$d
 modify(
   for $p in $c//pair[not(.//pair)] (: pairs with no descendant pairs :)  
   return insert node 
    <pair>
      <key>copy_{$p/key/string()}</key>
      <value>some new</value>
    </pair> 
   after $p
  )
  return $c
};