Re: Cost of complex match patterns

>> match="foo[//bar]"
>
>> match="foo"
>
>> Should the former be avoided, or because it's within a match
>> pattern it's converted to a simple lookup so it's fine?
>
>  I don't know the details of your processor on that point, but out of
> interest, if you only match on the main input tree, you can replace the
> former by:
>
>    <xsl:variable name="has-bar" as="xs:boolean" select="
>        exists(//bar)"/>
>
>    <xsl:template match="foo[$has-bar]">


Indeed (apart from 1.0 where you can't use variables in match
patterns)... the question I'm asking though is whether you need to
workaround potentially expensive match patterns (as they will be
evaluated per element), or whether through the inbuilt pattern
matching process it's actually a good idea to move work into the match
pattern.

For example,

match="foo[ancestor::bar/@type = 'A']"

and

match="foo[ancestor::bar/@type = 'B']"

 (or "bar[@type = 'A']//foo" but I prefer the above)

Is it better to pass down the type through parameters to avoid the
predicate, or is there no need to worry about it because it becomes a
simple lookup?

I'm pretty sure it's the latter....


-- 
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/