Re: [xsl] Cheaper to prepend or append an item to a sequence?

[Abel Braaksma <abel.online@xxxxxxxxx>]

PQQP5Q
P;P0P2,

Actually, it _is_ dependent on the current node. //@id gets all @id 
nodes in the document. The next "[..]" means "filter these nodes by the 
following expression". That expression is a node-test: 
"not(ancestor::meta)", which is applied to the _current_ node (the 
current @id-node).

That doesn't mean that a processor cannot optimize that, but in this 
case that might proof futile: no single element can contain multiple 
attributes with the same name. Hence the processor will have to test the 
predicate for each and every found id-attribute.

In short: no, it cannot be calculated only once.

Kind regards,
Abel Braaksm


On 22-2-2011 20:26, PQQP5Q
P;P0P2 P!P5P4P>P2 wrote:
> @id = //@id except (@id, //meta//@id) - yep... good idea
>
> but i think that even //@id[not(ancestor::meta)] should be calculated
> only once since it not depend from current node - is not it? is
> optimizer capable to recognize context dependant from context
> independant XPath fragments inside predicate and calculate independant
> fragments only once instead calculating it every time for each node?