Subject: Re: [xsl] Which XPath evaluates faster: count(../A) eq 1 or not( following-sibling::A) From: "Wolfgang Laun wolfgang.laun@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Tue, 4 Nov 2014 15:11:31 -0000 |
Apart from implementation dependent effects: IIRC, this has been discussed before, mentioning that a third variant using (the negation of) ../A[2] also has its merits - appears to skirt the counting issue. -W On 4 November 2014 15:57, Michael Kay mike@xxxxxxxxxxxx < xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > It depends entirely on the XPath processor you are using. > > For Saxon, I wouldn't expect to see a measurable difference. Unless there > happen to be 100,000 B elements before the A on which you are positioned, > in which case count(../A) might take rather longer. > > > Michael Kay > Saxonica > mike@xxxxxxxxxxxx > +44 (0) 118 946 5893 > > > > > On 4 Nov 2014, at 13:57, Costello, Roger L. costello@xxxxxxxxx < > xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > > Hi Folks, > > > > I am positioned in the XML tree at the first <A> element, within a > <parent> element. > > > > Requirement: There must be only one <A> element within <parent>. > > > > Here are two XPath expressions to check that there is only one <A> > element: > > > > count(../A) eq 1 > > > > or > > > > not(following-sibling::A) > > > > Which XPath expression evaluates faster? > > > > /Roger
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