Re: [xml] XPath / LibXML question

["Aron Stansvik" <elvstone gmail com>]

On 6/1/06, Alan_McCarthy scee net <Alan_McCarthy scee net> wrote:
> Hi,
>
> I have a question about XPath and have been pointed in the direction of
> this mailing list. Hope this is the correct place.
>
> I have the following XPath:
>
> /base/group/item[ att1=1]/instances/instance[ att2=2]
>
> and when used on my XML document it returns multiple items, e.g.
>
> /base[1]/group[1]/item[167]/instances[1]/instance[1] - result
> /base[1]/group[1]/item[195]/instances[1]/instance[1] - result
> /base[1]/group[1]/item[197]/instances[1]/instance[1] - result
> /base[1]/group[1]/item[202]/instances[1]/instance[1] - result
> /base[1]/group[1]/item[216]/instances[1]/instance[1] - result
>
> In this particular instance however, I only need to find one of the
> results, and it doesn't matter which one.
> For CPU efficiency I would like to find a way to do that.
> Does anyone know how I can achieve this, ideally by  modifying my XPath,
> but if that is not possible, if there are parameters, or context set up
> that could be done within LibXML to restrict it to one result.

You could use a predicate such as [position() = 1] to get the first
result. I don't know if this saves you anything performance-wise
though, one of the libxml2 hackers will have to answer that.

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Best regards,
Aron Stansvik