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 $isDbNode };
With the prof:dump() calls commented out as shown here, it always returns true, even when it returned false.
If I comment in the prof:dumps then I get the expected correct false result.
This must be the result some optimization at compile time but I haven’t been able to find a construction of this function that works without the debug messages.
Is there a better way to determine if a node is a database node?
This is with 10.6.
Cheers,
E. _____________________________________________ Eliot Kimber Sr Staff Content Engineer O: 512 554 9368 M: 512 554 9368 servicenow.comhttps://www.servicenow.com LinkedInhttps://www.linkedin.com/company/servicenow | Twitterhttps://twitter.com/servicenow | YouTubehttps://www.youtube.com/user/servicenowinc | Facebookhttps://www.facebook.com/servicenow
Hi Eliot,
The XQuery Specification allows implementations to simplify an expression if it always yields the same result in the case of success. As db:node-id never returns an empty sequence, BaseX rewrites exists(db:node-id()) to true().
You can use the following alternative:
declare function util:isDatabaseNode($node) { try { boolean(db:name($node)) } catch db:node { false() } };
It would be cleaner if we added a dedicated function for that in a future version of BaseX.
Cheers, Christian
On Mon, Jul 3, 2023 at 9:55 PM Eliot Kimber eliot.kimber@servicenow.com wrote:
I need to be able to determine if an arbitrary node is or is not a database node.
I implemented this function:
declare function util:isDatabaseNode($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 $isDbNode
};
With the prof:dump() calls commented out as shown here, it always returns true, even when it returned false.
If I comment in the prof:dumps then I get the expected correct false result.
This must be the result some optimization at compile time but I haven’t been able to find a construction of this function that works without the debug messages.
Is there a better way to determine if a node is a database node?
This is with 10.6.
Cheers,
E.
Eliot Kimber
Sr Staff Content Engineer
O: 512 554 9368
M: 512 554 9368
servicenow.com
LinkedIn | Twitter | YouTube | Facebook
Thanks for the tip.
A db:is-node() function would be most handy.
In my case, I’m using transform with to augment content pulled from the database before doing processing that will vary depending on whether I have a database node (i.e., getting its node ID or database path) or I don’t.
Of course it would also be useful for functions that may operate on database nodes or content parsed from the file system.
Cheers,
Eliot
_____________________________________________ Eliot Kimber Sr Staff Content Engineer O: 512 554 9368 M: 512 554 9368 servicenow.comhttps://www.servicenow.com LinkedInhttps://www.linkedin.com/company/servicenow | Twitterhttps://twitter.com/servicenow | YouTubehttps://www.youtube.com/user/servicenowinc | Facebookhttps://www.facebook.com/servicenow
From: Christian Grün christian.gruen@gmail.com Date: Tuesday, July 4, 2023 at 4:14 AM To: Eliot Kimber eliot.kimber@servicenow.com Cc: basex-talk@mailman.uni-konstanz.de basex-talk@mailman.uni-konstanz.de Subject: Re: [basex-talk] Determining if a node is a database node [External Email]
Hi Eliot,
The XQuery Specification allows implementations to simplify an expression if it always yields the same result in the case of success. As db:node-id never returns an empty sequence, BaseX rewrites exists(db:node-id()) to true().
You can use the following alternative:
declare function util:isDatabaseNode($node) { try { boolean(db:name($node)) } catch db:node { false() } };
It would be cleaner if we added a dedicated function for that in a future version of BaseX.
Cheers, Christian
On Mon, Jul 3, 2023 at 9:55 PM Eliot Kimber eliot.kimber@servicenow.com wrote:
I need to be able to determine if an arbitrary node is or is not a database node.
I implemented this function:
declare function util:isDatabaseNode($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
servicenow.com
LinkedIn | Twitter | YouTube | Facebook
Maybe we still need to find better terms than »database node« and »fragments« to describe the data structures that we use for XML structures (as described in [1]), as the current situation is even more complex:
1. we have fragments (e.g. as the result of <x/>) 2. we have volatile main-memory database nodes 3. we have persistent database nodes
…and db:node-id can only be used for persistent database nodes.
In my case, I’m using transform with to augment content pulled from the database before doing processing that will vary depending on whether I have a database node (i.e., getting its node ID or database path) or I don’t.
Feel free to provide us with a little use case.
[1] https://docs.basex.org/wiki/Database_Module#Database_Nodes
basex-talk@mailman.uni-konstanz.de
-
Christian Grün -
Eliot Kimber