Hi Eliot,
The XQuery Specification allows implementations to simplify an
expression if it always yields the same result in the case of success.
As db:node-id never returns an empty sequence, BaseX rewrites
exists(db:node-id()) to true().
You can use the following alternative:
declare function util:isDatabaseNode($node) {
try {
boolean(db:name($node))
} catch db:node {
false()
}
};
It would be cleaner if we added a dedicated function for that in a
future version of BaseX.
Cheers,
Christian
On Mon, Jul 3, 2023 at 9:55 PM Eliot Kimber <eliot.kim...@servicenow.com> wrote:
>
> I need to be able to determine if an arbitrary node is or is not a database
> node.
>
>
>
> I implemented this function:
>
> declare function util:isDatabaseNode($node as node()) as xs:boolean {
>
> let $isDbNode as xs:boolean :=
>
> try {
>
> let $nodeId as xs:integer? := db:node-id($node)
>
> (: let $msg := prof:dump(``[[DEBUG] relpath:isDatabaseNode(): nodeId:
> "`{$nodeId}`"]``) :)
>
> return exists($nodeId)
>
> } catch * {
>
> (: let $msg := prof:dump(``[[DEBUG] relpath:isDatabaseNode(): Got
> exception `{$err:code}` - `{$err:description}`]``) :)
>
> (: return :) false()
>
> }
>
> let $msg := prof:dump(``[[DEBUG] relpath:isDatabaseNode(): Returning
> `{$isDbNode}``]``)
>
> return $isDbNode
>
> };
>
>
>
> With the prof:dump() calls commented out as shown here, it always returns
> true, even when it returned false.
>
>
>
> If I comment in the prof:dumps then I get the expected correct false result.
>
>
>
> This must be the result some optimization at compile time but I haven’t been
> able to find a construction of this function that works without the debug
> messages.
>
>
>
> Is there a better way to determine if a node is a database node?
>
>
>
> This is with 10.6.
>
>
>
> Cheers,
>
>
>
> E.
>
> _____________________________________________
>
> Eliot Kimber
>
> Sr Staff Content Engineer
>
> O: 512 554 9368
>
> M: 512 554 9368
>
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>
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