Re: [xsl] XPath Expressions: Separate predicates or one predicate with AND?

["Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

> But it occurs to me that in this case the expressions are functionally
identical: the set of predicates is effectively an AND group.

> Is there any reason to prefer one form expression over the other?

No, but the ordering of the sub-expressions (assuming the processor
does shortcuts) can be really important. That is, place first the
sub-expression that most-often would make the whole expression false()
(in case of "and"-ing) or true() (in case of "or"-ing).

I believe that shortcutting isn't specified as mandatory in the XPath
specifications, but I might be wrong. Certainly, any serious optimizer
will do shortcutting.


Cheers,
Dimitre

On Tue, Feb 21, 2017 at 2:07 PM, Eliot Kimber ekimber@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> Ibm updating code that has expressions like:
>
> <xsl:when test=b*[@a = b1b and @b = b2b and @c = b3b]b>
>
> My normal practice would be to use separate predicates:
>
> <xsl:when test=b*[@a = b1b][@b = b2b][@c = b3b]b>
>
> But it occurs to me that in this case the expressions are functionally
identical: the set of predicates is effectively an AND group.
>
> Is there any reason to prefer one form expression over the other?
>
> I can imagine that different XSLT processors might apply different
optimization strategies to the two forms, although as webve discussed many
times, thatbs not something you can worry about for general usage.
>
> Cheers,
>
> Eliot
>
>
>
> --
> Eliot Kimber
> http://contrext.com
>
>
>



--
Cheers,
Dimitre Novatchev
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